Secondary thickening hi-res stock photography and images

Banyan Tree with several trunks Stock Photo

RFCYH4D1–Banyan Tree with several trunks

Broom stem. Light micrograph (LM) of a transverse section through the stem of a common broom (Salicornia europaea) plant. Stock Photo

RF2DYDW02–Broom stem. Light micrograph (LM) of a transverse section through the stem of a common broom (Salicornia europaea) plant.

Transactions of the Royal Society of New Zealand . rransverse petiole, young plant ofM. excelsum : b, dorsal; a, ventralside; c, bundle. X 44. Root—Macropiper excelsum. In M. excelsum the roots are adventitious. The primary root is veryearly lost. On uprooting the plant one finds it characteristically forked.Very often a seedling bearing- only the two cotyledons has lost its primaryroot. [ronside.—Anatomical Structure of N.Z. Piperaceae. 345 The structure was carefully examined. Secondary thickening is deve-loped to a marked degree, and is especially noticeable near the base of thestem. The bu Stock Photo

RM2AM8186–Transactions of the Royal Society of New Zealand . rransverse petiole, young plant ofM. excelsum : b, dorsal; a, ventralside; c, bundle. X 44. Root—Macropiper excelsum. In M. excelsum the roots are adventitious. The primary root is veryearly lost. On uprooting the plant one finds it characteristically forked.Very often a seedling bearing- only the two cotyledons has lost its primaryroot. [ronside.—Anatomical Structure of N.Z. Piperaceae. 345 The structure was carefully examined. Secondary thickening is deve-loped to a marked degree, and is especially noticeable near the base of thestem. The bu

. Fossil plants : for students of botany and geology . Paleobotany. xxv] ANKYROPTERIS 459 sieve-tubes, Sv, and the flattened cells resemble tissues in a corresponding position in the steles of modern Osmundaceae. In a section of Ankyropteris corrugata in the Williamson Collection the radial arrangement of the more external meta- xylem elements suggests the addition of secondary tracheae'. This suggestion of secondary thickening, a point which requires much more thorough investigation, is interesting in relation to a new type of stem named by Scott Botrychioxylon^, but not yet fully described. Stock Photo

RMPG14Y2–. Fossil plants : for students of botany and geology . Paleobotany. xxv] ANKYROPTERIS 459 sieve-tubes, Sv, and the flattened cells resemble tissues in a corresponding position in the steles of modern Osmundaceae. In a section of Ankyropteris corrugata in the Williamson Collection the radial arrangement of the more external meta- xylem elements suggests the addition of secondary tracheae'. This suggestion of secondary thickening, a point which requires much more thorough investigation, is interesting in relation to a new type of stem named by Scott Botrychioxylon^, but not yet fully described.

The elements of botany for The elements of botany for beginners and for schools elementsofbotany00gray Year: 1887 36 ROOTS. [SECTION 5. Spindle-shaped, or Fusiform, when thickest in the middle and tapering to both ends; as the common Radish (Fig. 85). 76. These examples are of primary roots. It will be seen that turnips, carrots, and tne like, are not pure root throughout ; l'or the caulicle, from the lower end of which the root grew, partakes oi me thickening, perhaps also some joints of stem above: so the bud-bearing and growing top is stem. 77. A fine example of secondary roots (67), some Stock Photo

RMRWMXC9–The elements of botany for The elements of botany for beginners and for schools elementsofbotany00gray Year: 1887 36 ROOTS. [SECTION 5. Spindle-shaped, or Fusiform, when thickest in the middle and tapering to both ends; as the common Radish (Fig. 85). 76. These examples are of primary roots. It will be seen that turnips, carrots, and tne like, are not pure root throughout ; l'or the caulicle, from the lower end of which the root grew, partakes oi me thickening, perhaps also some joints of stem above: so the bud-bearing and growing top is stem. 77. A fine example of secondary roots (67), some

RF2DYDW0F–Broom stem. Light micrograph (LM) of a transverse section through the stem of a common broom (Salicornia europaea) plant.

. Journal of morphology . a name that was applied byClaparede to a structure which appears later, and which has beenidentified as the caudal thickening. Kishinouye, to avoid the con-fusion arising from applying the same name to different structures,has called it the primary thickening, which name seems l:>estadapted to this purpose. 4. Formation of the Caudal, or Secondary, Thickening.—Shortlyafter the formation of the primary thickening, a second thickening isformed which appears as an elevation of the blastodisc near the edgeof the blastopore. This elevation is caused by a rapid accumulat Stock Photo

RM2CDG1WY–. Journal of morphology . a name that was applied byClaparede to a structure which appears later, and which has beenidentified as the caudal thickening. Kishinouye, to avoid the con-fusion arising from applying the same name to different structures,has called it the primary thickening, which name seems l:>estadapted to this purpose. 4. Formation of the Caudal, or Secondary, Thickening.—Shortlyafter the formation of the primary thickening, a second thickening isformed which appears as an elevation of the blastodisc near the edgeof the blastopore. This elevation is caused by a rapid accumulat

. Studies in fossil botany . Paleobotany. 146 STUDIES IN FOSSIL BOTANY forms, the development of the xylem must have been centripetal. Immediately within the protoxylem the elements become much larger, forming a broad continu- ous zone, which consists exclusively of long scalariform tracheides, without any admixture of parenchyma (Figs.. "«:#, Fig. 60.—Lepidodendron selaginoides. Transverse section of stele after commencement of secondary thickening. .*:, primary xylem-cylinder, with reticulate tracheides in central part, and small protoxylem-elements at periphery ; jr2, secondary wood, u Stock Photo

RMPG175M–. Studies in fossil botany . Paleobotany. 146 STUDIES IN FOSSIL BOTANY forms, the development of the xylem must have been centripetal. Immediately within the protoxylem the elements become much larger, forming a broad continu- ous zone, which consists exclusively of long scalariform tracheides, without any admixture of parenchyma (Figs.. "«:#, Fig. 60.—Lepidodendron selaginoides. Transverse section of stele after commencement of secondary thickening. .*:, primary xylem-cylinder, with reticulate tracheides in central part, and small protoxylem-elements at periphery ; jr2, secondary wood, u

. Memoirs and proceedings of the Manchester Literary & Philosophical Society. ws of meristem aroundcentral region; a, central primary xylem : b1, base of xylemof leaf-trace ; P, outer xylem ; px, protoxylem ; <r, xylem sheath ;d, primary phloem ; e, secondary prismatic tissue; /, meristem ;g, cortical tissue. Photo i. Median longitudinal section of the stem of a well-grown stock, in which the primary stele is surroundedby a zone of anomalous secondary thickening. ( x 67.) Photo 2. Median longitudinal section of the stem of an equallylarge plant, in which, however, no anomalous secondarythic Stock Photo

RM2CEKH27–. Memoirs and proceedings of the Manchester Literary & Philosophical Society. ws of meristem aroundcentral region; a, central primary xylem : b1, base of xylemof leaf-trace ; P, outer xylem ; px, protoxylem ; <r, xylem sheath ;d, primary phloem ; e, secondary prismatic tissue; /, meristem ;g, cortical tissue. Photo i. Median longitudinal section of the stem of a well-grown stock, in which the primary stele is surroundedby a zone of anomalous secondary thickening. ( x 67.) Photo 2. Median longitudinal section of the stem of an equallylarge plant, in which, however, no anomalous secondarythic

. Fossil plants : for students of botany and geology . Paleobotany. X] ARTHROPITYS. 313 result of active growth, and not merely the expression of the tangential stretching of the stem consequent on secondary thickening. A glance at the complete transverse section of the stem,— of which a small portion is shown in fig. 74 A,—suggests the existence of annual rings in the wood, but this appearance of rings is merely the result of compression. The secondary wood of a Calamite does not exhibit any regular zones of growth comparable with the annual rings of our forest trees.. Fig. 75. Longitudinal t Stock Photo

RMPG16FE–. Fossil plants : for students of botany and geology . Paleobotany. X] ARTHROPITYS. 313 result of active growth, and not merely the expression of the tangential stretching of the stem consequent on secondary thickening. A glance at the complete transverse section of the stem,— of which a small portion is shown in fig. 74 A,—suggests the existence of annual rings in the wood, but this appearance of rings is merely the result of compression. The secondary wood of a Calamite does not exhibit any regular zones of growth comparable with the annual rings of our forest trees.. Fig. 75. Longitudinal t

. Memoirs and proceedings of the Manchester Literary & Philosophical Society. • KV -.. & * t k. ■ l1 • 1!? ^ 1 U nWtX*&£* iA. 56 LANG, Stele of the Shoot of hottes lacustris. PLATE IV. Photo 14. Slightly oblique transverse section of a stele withoutevident secondary thickening, showing the generalstructure, the continuity of primary phloem from leaf-trace to stem and the deep insertion of the leaf-tracexylem into the xylem of the stele. From the sameplant as the Photos in Plate III. ( x 67.) Photo 15. Continuity of primary phloem followed from stemto leaf-trace in a stem without any secondary Stock Photo

RM2CEKG9E–. Memoirs and proceedings of the Manchester Literary & Philosophical Society. • KV -.. & * t k. ■ l1 • 1!? ^ 1 U nWtX*&£* iA. 56 LANG, Stele of the Shoot of hottes lacustris. PLATE IV. Photo 14. Slightly oblique transverse section of a stele withoutevident secondary thickening, showing the generalstructure, the continuity of primary phloem from leaf-trace to stem and the deep insertion of the leaf-tracexylem into the xylem of the stele. From the sameplant as the Photos in Plate III. ( x 67.) Photo 15. Continuity of primary phloem followed from stemto leaf-trace in a stem without any secondary

. Studies in fossil botany . Paleobotany. 22 STUDIES IN FOSSIL BOTANY preserved at the very commencement, or even before the commencement, of secondary growth, as shown in Fig. 5. This is a comparatively rare stage to find, and when it is found, it is nearly always in a small twig. The larger stems of Catamites are rarely, if ever, met with at so early a stage of development. In a twig in this early condition, before secondary thickening has begun, the pith is often persistent (though fistular in the specimen figured), and round it we find a ring of. Fig. 5.—Calaviites, sp. Transverse section Stock Photo

RMPG17A5–. Studies in fossil botany . Paleobotany. 22 STUDIES IN FOSSIL BOTANY preserved at the very commencement, or even before the commencement, of secondary growth, as shown in Fig. 5. This is a comparatively rare stage to find, and when it is found, it is nearly always in a small twig. The larger stems of Catamites are rarely, if ever, met with at so early a stage of development. In a twig in this early condition, before secondary thickening has begun, the pith is often persistent (though fistular in the specimen figured), and round it we find a ring of. Fig. 5.—Calaviites, sp. Transverse section

. Comparative anatomy of the vegetative organs of the phanerogams and ferns. Plant anatomy; Phanerogams; Ferns. SECONDARY THICKENING. NORMAL DICOTYLEDONS. 455 duced from it, which constitute the secondary thickening, are in the main outlines the same in the very great majority of stems of Dicotyledons and Gymnosperms. The phenomena belonging to this category, to be treated of in the present Chapter, may therefore be termed those of the normal growih in thickness, and the stems in question be termed the normal stems, while those showing a different behaviour may be contrasted with them, as ano? Stock Photo

RMREFEH7–. Comparative anatomy of the vegetative organs of the phanerogams and ferns. Plant anatomy; Phanerogams; Ferns. SECONDARY THICKENING. NORMAL DICOTYLEDONS. 455 duced from it, which constitute the secondary thickening, are in the main outlines the same in the very great majority of stems of Dicotyledons and Gymnosperms. The phenomena belonging to this category, to be treated of in the present Chapter, may therefore be termed those of the normal growih in thickness, and the stems in question be termed the normal stems, while those showing a different behaviour may be contrasted with them, as ano?

. Fossil plants : for students of botany and geology . Paleobotany. ABC Pig. 140. Picea excelsa. Shoots of different ages showing changes in the appear- ance of the leaf-cushions: a leaf attached to a cushion in fig. A. (Slightly enlarged.) A portion of the cushion below the triangular leaf-scar often shows transverse gaping cracks or depressions (fig. 185, C) such as occur on a smaller scale on the older cushions of a Fir twig (fig. 140). Secondary thickening, as in recent trees, is not confined to the vascular cylinder but at an early stage, frequently before there are any signs of secondary Stock Photo

RMPG0DBX–. Fossil plants : for students of botany and geology . Paleobotany. ABC Pig. 140. Picea excelsa. Shoots of different ages showing changes in the appear- ance of the leaf-cushions: a leaf attached to a cushion in fig. A. (Slightly enlarged.) A portion of the cushion below the triangular leaf-scar often shows transverse gaping cracks or depressions (fig. 185, C) such as occur on a smaller scale on the older cushions of a Fir twig (fig. 140). Secondary thickening, as in recent trees, is not confined to the vascular cylinder but at an early stage, frequently before there are any signs of secondary

. Comparative anatomy of the vegetative organs of the phanerogams and ferns;. Plant anatomy; Ferns. SECONDARY THICKENING. NORMAL DICOTYLEDONS. 493 canals often arise in them'; in the wood of Prunus avium, they are, according to Wigand ^, a principal starting-point of the disorganisation which produces the cherry- gum. The dilatations of the medullary rays and the medullary spots occur, it is true, relatively seldom ; they are, however, characteristic of many woods, both Dicotyledonous and Coniferous. Ac- cording to Kraus and Nordlinger they have been frequently observed in Betula alba, dahuric Stock Photo

RMRE2N99–. Comparative anatomy of the vegetative organs of the phanerogams and ferns;. Plant anatomy; Ferns. SECONDARY THICKENING. NORMAL DICOTYLEDONS. 493 canals often arise in them'; in the wood of Prunus avium, they are, according to Wigand ^, a principal starting-point of the disorganisation which produces the cherry- gum. The dilatations of the medullary rays and the medullary spots occur, it is true, relatively seldom ; they are, however, characteristic of many woods, both Dicotyledonous and Coniferous. Ac- cording to Kraus and Nordlinger they have been frequently observed in Betula alba, dahuric

. Studies in fossil botany . Paleobotany. STIGMARIA 255 however, we find an addition of radially arranged secondary wood (see Fig. 104, 3?), and where this is the case the secondary formation is always limited to the side remote from the protoxylem, thus affording yet another indication of monarch structure. The formation of secondary wood, though rare in the free rootlets, is. JOX. DC Fig. 104.—Stigmaria ficoides. Transverse section o central part of rootlet, to show secondary thickening of wood, jr, primary xylem ; px, protoxylem ; -r2, secondary xylem, limited to one side of bundle ; i.c, i Stock Photo

RMPG16YP–. Studies in fossil botany . Paleobotany. STIGMARIA 255 however, we find an addition of radially arranged secondary wood (see Fig. 104, 3?), and where this is the case the secondary formation is always limited to the side remote from the protoxylem, thus affording yet another indication of monarch structure. The formation of secondary wood, though rare in the free rootlets, is. JOX. DC Fig. 104.—Stigmaria ficoides. Transverse section o central part of rootlet, to show secondary thickening of wood, jr, primary xylem ; px, protoxylem ; -r2, secondary xylem, limited to one side of bundle ; i.c, i

. Comparative anatomy of the vegetative organs of the phanerogams and ferns;. Plant anatomy; Ferns. SECONDARY THICKENING. NORMAL DICOTYLEDONS. 455 duced from it, which constitute the secondary thickening, are in the main outlines the same in the very great majority of stems of Dicotyledons and Gymnosperms. The phenomena belonging to this category, to be treated of in the present Chapter, may therefore be termed those of the normal growth in thickness., and the stems in question- be termed the normal* stems, while those showing a different behaviour may be contrasted with them, as anomalous for Stock Photo

RMRE2NAP–. Comparative anatomy of the vegetative organs of the phanerogams and ferns;. Plant anatomy; Ferns. SECONDARY THICKENING. NORMAL DICOTYLEDONS. 455 duced from it, which constitute the secondary thickening, are in the main outlines the same in the very great majority of stems of Dicotyledons and Gymnosperms. The phenomena belonging to this category, to be treated of in the present Chapter, may therefore be termed those of the normal growth in thickness., and the stems in question- be termed the normal* stems, while those showing a different behaviour may be contrasted with them, as anomalous for

. Studies in fossil botany . Paleobotany. THE STEM OF CALAMITES 25 far as anatomy goes, is simply an Equisetum with secondary thickening. In order to carry the comparison further, we must settle one or two points, especially the course of the vascular bundles. In Equisetum itself their course is exceedingly simple: a single vascular bundle enters the stem from each leaf, and. Fig. 7.—Calamitcs, sp. Radial section of a decorticated stem, with fairly thick wood, showing the fistular pith, crossed by diaphragms at the nodes. X 9. From a photo- graph. Phil. Trans., W. and S. Will. Coll. 1937. pass Stock Photo

RMPG179P–. Studies in fossil botany . Paleobotany. THE STEM OF CALAMITES 25 far as anatomy goes, is simply an Equisetum with secondary thickening. In order to carry the comparison further, we must settle one or two points, especially the course of the vascular bundles. In Equisetum itself their course is exceedingly simple: a single vascular bundle enters the stem from each leaf, and. Fig. 7.—Calamitcs, sp. Radial section of a decorticated stem, with fairly thick wood, showing the fistular pith, crossed by diaphragms at the nodes. X 9. From a photo- graph. Phil. Trans., W. and S. Will. Coll. 1937. pass

. Comparative anatomy of the vegetative organs of the phanerogams and ferns;. Plant anatomy; Ferns. SECONDARY THICKENING. NORMAL DICOTYLEDONS. 465 The structure of the cambium, and of the young wood and bast, has been given above, as regards the arrangement of the cells when seen in cross-section. In each portion of the cambial zone, the form of the cells is identical with or similar to the general form of the elements of that section of the mature wood and bast which borders on it in the radial direction. (Figs. 198, 199.) Parenchymatous medullary rays are bordered by portions of the cambium, Stock Photo

RMRE2NAD–. Comparative anatomy of the vegetative organs of the phanerogams and ferns;. Plant anatomy; Ferns. SECONDARY THICKENING. NORMAL DICOTYLEDONS. 465 The structure of the cambium, and of the young wood and bast, has been given above, as regards the arrangement of the cells when seen in cross-section. In each portion of the cambial zone, the form of the cells is identical with or similar to the general form of the elements of that section of the mature wood and bast which borders on it in the radial direction. (Figs. 198, 199.) Parenchymatous medullary rays are bordered by portions of the cambium,

. Fossil plants : for students of botany and geology . Paleobotany. Fig. 91. A. Diagrammatic sketch of a transverse section of a young root of Galamites. x, xylem; I, lacuna. After Hick. B. Central cylinder (stele) of root, px, protoxylem; ph, phloem; x^, secondary xylem; I, phloeoterma. x 75. After Williamson and Scott. the figure secondary thickening has begun, and the cambial cells internal to each phloem group have given rise to a few radially disposed tracheids, x Beyond the phloem there are two layers of parenchyma representing, as regards position, a pericycle and an endodermis. In the Stock Photo

RMPG0DA8–. Fossil plants : for students of botany and geology . Paleobotany. Fig. 91. A. Diagrammatic sketch of a transverse section of a young root of Galamites. x, xylem; I, lacuna. After Hick. B. Central cylinder (stele) of root, px, protoxylem; ph, phloem; x^, secondary xylem; I, phloeoterma. x 75. After Williamson and Scott. the figure secondary thickening has begun, and the cambial cells internal to each phloem group have given rise to a few radially disposed tracheids, x Beyond the phloem there are two layers of parenchyma representing, as regards position, a pericycle and an endodermis. In the

. Contributions from the Botanical Laboratory of the University of Pennsylvania. Plants; Plants -- Pennsylvania. Monotropaceae with Reference to Ericaceae 61 but this is rare. The walls of the outer cells of the cortex also become thickened and these also fall off. Meantime the 4-5 arch bundle system has undergone secondary thickening. New xylem cells have developed so that there is formed a solid central cylinder of wood enclosed by a few layers of thin-walled phloem cells. These roots are perennial and annual rings of wood are laid down. The oldest one examined was found to have four years o Stock Photo

RMRE9PRN–. Contributions from the Botanical Laboratory of the University of Pennsylvania. Plants; Plants -- Pennsylvania. Monotropaceae with Reference to Ericaceae 61 but this is rare. The walls of the outer cells of the cortex also become thickened and these also fall off. Meantime the 4-5 arch bundle system has undergone secondary thickening. New xylem cells have developed so that there is formed a solid central cylinder of wood enclosed by a few layers of thin-walled phloem cells. These roots are perennial and annual rings of wood are laid down. The oldest one examined was found to have four years o

. The pathology and differential diagnosis of infectious diseases of animals : prepared for students and practitioners of veterinary medicine . Veterinary medicine; Communicable diseases in animals. 122 GLANDERS lymph glands becomes infiltrated •with small cells and subsequently thickened. In rare cases secondary chronic farcy occurs. It is marked by a large, diffuse new growth of connective tissue with nodular thickening of the skin. This condition is termed glander- ous elephantiasis or pachyderma. It chiefly affects the limbs and head. Of the abdominal organs, the spleen is most frequently Stock Photo

RMPG2NM4–. The pathology and differential diagnosis of infectious diseases of animals : prepared for students and practitioners of veterinary medicine . Veterinary medicine; Communicable diseases in animals. 122 GLANDERS lymph glands becomes infiltrated •with small cells and subsequently thickened. In rare cases secondary chronic farcy occurs. It is marked by a large, diffuse new growth of connective tissue with nodular thickening of the skin. This condition is termed glander- ous elephantiasis or pachyderma. It chiefly affects the limbs and head. Of the abdominal organs, the spleen is most frequently

RMREFEE7–. Comparative anatomy of the vegetative organs of the phanerogams and ferns. Plant anatomy; Phanerogams; Ferns. SECONDARY THICKENING. NORMAL DICOTYLEDONS. 521 the cambium, remained for a long time extremely obscure, and the accurate repre- sentations given by Th. Hartig as early as 1837 failed to be understood, until Mohl, in 1855 ^ brought them into deserved honour. For the same reasons later investi- gations often leave much to be desired, and the special anatomy of the bast is but insufficiently treated of by most authors. Sect. 162. The main fundamental mass of the medullary rays always co

. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative. EYE 209 centripetally towards the brain; centrifugal fibres also arise later. In the course of further development, the epiblastic thickening mentioned above, which is often at first hollow, becomes separated from the epiblast, sinks more and more into the interior of the optic vesicle, and is diflferentiated to form the crystalline lens (Fig 167, b). The remaining space within the optic vesicle becomes filled by mesoblastic tissue, which grows in from the ventral side of the secondary optic vesicle through the so-call Stock Photo

RMPG2MW0–. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative. EYE 209 centripetally towards the brain; centrifugal fibres also arise later. In the course of further development, the epiblastic thickening mentioned above, which is often at first hollow, becomes separated from the epiblast, sinks more and more into the interior of the optic vesicle, and is diflferentiated to form the crystalline lens (Fig 167, b). The remaining space within the optic vesicle becomes filled by mesoblastic tissue, which grows in from the ventral side of the secondary optic vesicle through the so-call

. Comparative anatomy of the vegetative organs of the phanerogams and ferns;. Plant anatomy; Ferns. SECONDARy THICKENING. NORMAL DICOVrLEDONS. 53^ zones of secondary growth, to the non-equivalent members, and to individual dif- ferences, there is far less to be said in the case of the bast than in that of the wood, partly, no doubt, owing to the really greater simplicity of the phenomena, partly because it is better to pass over a number of the known changes and to discuss them in the next chapter, and lastly, in no small degree, because, for reasons already stated above, there is still an abs Stock Photo

RMRE2N8F–. Comparative anatomy of the vegetative organs of the phanerogams and ferns;. Plant anatomy; Ferns. SECONDARy THICKENING. NORMAL DICOVrLEDONS. 53^ zones of secondary growth, to the non-equivalent members, and to individual dif- ferences, there is far less to be said in the case of the bast than in that of the wood, partly, no doubt, owing to the really greater simplicity of the phenomena, partly because it is better to pass over a number of the known changes and to discuss them in the next chapter, and lastly, in no small degree, because, for reasons already stated above, there is still an abs

. A text-book of botany for secondary schools. Botany. Fig. 72.—Diagrammatic cross-aection of a young root, showing the innermost layer of the cortex (c) and the vascu- lar cylinder (v) containing alternating regions of xylem (x) and phloem (p).. Fig. 73.—Diagram showing the method of thickening the vascular cylinder of a root: A represents the cross-section of a young root in which four phloem strands (p) alternate with four xylem strands (x), the whole bundle region being enveloped by the thick cortex ; B represents an older root in which there is a continuous zone of cambium (c), which is f Stock Photo

RMPFYF2K–. A text-book of botany for secondary schools. Botany. Fig. 72.—Diagrammatic cross-aection of a young root, showing the innermost layer of the cortex (c) and the vascu- lar cylinder (v) containing alternating regions of xylem (x) and phloem (p).. Fig. 73.—Diagram showing the method of thickening the vascular cylinder of a root: A represents the cross-section of a young root in which four phloem strands (p) alternate with four xylem strands (x), the whole bundle region being enveloped by the thick cortex ; B represents an older root in which there is a continuous zone of cambium (c), which is f

. A textbook of botany for colleges and universities ... Botany. 248 MORPHOLOGY is of the most primitive type, being solid (with xylem at the center) and exarch. However, it is not concentric, the xylem developing towards the center from two or more protoxylem points near the periphery of the stele, and between these radiating strands of xylem separate phloem strands occur (fig. 555). This arrangement of phloem and xylem, in which they occur on alternating radii, is called the radial arrangement. In the secondary thickening of roots (figs. 556, 557), a cambium is developed, which forms seconda Stock Photo

RMRDYE8A–. A textbook of botany for colleges and universities ... Botany. 248 MORPHOLOGY is of the most primitive type, being solid (with xylem at the center) and exarch. However, it is not concentric, the xylem developing towards the center from two or more protoxylem points near the periphery of the stele, and between these radiating strands of xylem separate phloem strands occur (fig. 555). This arrangement of phloem and xylem, in which they occur on alternating radii, is called the radial arrangement. In the secondary thickening of roots (figs. 556, 557), a cambium is developed, which forms seconda

. Comparative anatomy of the vegetative organs of the phanerogams and ferns. Plant anatomy; Phanerogams; Ferns. SECONDARY THICKENING IN MONOCOTYLEDONS. 619 been differentiated, and are situated 14-18 and 20^"'", or many internodes belov/ the slowly elongating apex. The initial layer of the cambium is a layer of parenchyma- tous cells characterised by no further peculiarities, which runs round the outer surface of the bundle-cylinder, and is thus extrafascicular. It is in close proximity to the outermost leaf-trace bundles, and must doubtless be regarded as belonging to the plerome-cy Stock Photo

RMREFE85–. Comparative anatomy of the vegetative organs of the phanerogams and ferns. Plant anatomy; Phanerogams; Ferns. SECONDARY THICKENING IN MONOCOTYLEDONS. 619 been differentiated, and are situated 14-18 and 20^"'", or many internodes belov/ the slowly elongating apex. The initial layer of the cambium is a layer of parenchyma- tous cells characterised by no further peculiarities, which runs round the outer surface of the bundle-cylinder, and is thus extrafascicular. It is in close proximity to the outermost leaf-trace bundles, and must doubtless be regarded as belonging to the plerome-cy

RMREFEDE–. Comparative anatomy of the vegetative organs of the phanerogams and ferns. Plant anatomy; Phanerogams; Ferns. SECONDARY THICKENING. NORMAL DICOTYLEDONS. 5^3 In the bast of Dicotyledonous woody plants, the arrangement of the two kinds of tissue, so far as can be decided from the existing data, is less regular than in the Coniferous woods first mentioned, owing to the fact that the tangential series of the one form of tissue are sometimes single, sometimes double or multiple, and are interrupted by interpolated elements of the other form; while the average width of the adjoining tissue-element

. An introduction to the structure and reproduction of plants. Plant anatomy; Plants. 312 REPRODUCTION OF EOUISETUM genus as a whole is derived from aquatic ancestors. Indeed there is good eidence that the Calamites of the Coal Measures, which exhibited similar aquatic features combined with pro- nounced secondary thickening, were inhabitants of swamps. The sporangia of Horsetails are borne on little mushroom- shaped sporophylls (Fig. 176, B), differing widely from the. Fig. 175.—Common forms of prescr'ation of the fossil Horsetails and Clubmcsses. A, Pith-cast of Caltniules, B, Annularia sp Stock Photo

RMRDWP87–. An introduction to the structure and reproduction of plants. Plant anatomy; Plants. 312 REPRODUCTION OF EOUISETUM genus as a whole is derived from aquatic ancestors. Indeed there is good eidence that the Calamites of the Coal Measures, which exhibited similar aquatic features combined with pro- nounced secondary thickening, were inhabitants of swamps. The sporangia of Horsetails are borne on little mushroom- shaped sporophylls (Fig. 176, B), differing widely from the. Fig. 175.—Common forms of prescr'ation of the fossil Horsetails and Clubmcsses. A, Pith-cast of Caltniules, B, Annularia sp

. Comparative anatomy of the vegetative organs of the phanerogams and ferns;. Plant anatomy; Ferns. SECONDARY THICKENING IN MONOCOTYLEDONS. 619 been differentiated, and are situated 14-18 and 2oÂ«'n, or many internodes below the slowly elongating apex. The initial layer of the cambium is a layer of parenchyma- tous cells characterised by no further peculiarities, which runs round the outer surface of the bundle-cylinder, and is thus extrafascicular. It is in close proximity to the outermost leaf-trace bundles, and must doubtless be regarded as belonging to the plerome-cylinder. Radial growth o Stock Photo

RMRE2N45–. Comparative anatomy of the vegetative organs of the phanerogams and ferns;. Plant anatomy; Ferns. SECONDARY THICKENING IN MONOCOTYLEDONS. 619 been differentiated, and are situated 14-18 and 2oÂ«'n, or many internodes below the slowly elongating apex. The initial layer of the cambium is a layer of parenchyma- tous cells characterised by no further peculiarities, which runs round the outer surface of the bundle-cylinder, and is thus extrafascicular. It is in close proximity to the outermost leaf-trace bundles, and must doubtless be regarded as belonging to the plerome-cylinder. Radial growth o

. Comparative anatomy of the vegetative organs of the phanerogams and ferns;. Plant anatomy; Ferns. SECONDARY THICKENING, NORMAL DICOTYLEDONS. 5^3 In the bast of Dicotyledonous woody plants, the arrangement of the two kinds of tissue, so far as can be decided from the existing data, is less regular than in the Coniferous woods first mentioned, owing to the fact that the tangential series of the one form of tissue are sometimes single, sometimes double or multiple, and are interrupted by interpolated elements of the other form; while the average width of the adjoining tissue-elements of the two Stock Photo

RMRE2N8N–. Comparative anatomy of the vegetative organs of the phanerogams and ferns;. Plant anatomy; Ferns. SECONDARY THICKENING, NORMAL DICOTYLEDONS. 5^3 In the bast of Dicotyledonous woody plants, the arrangement of the two kinds of tissue, so far as can be decided from the existing data, is less regular than in the Coniferous woods first mentioned, owing to the fact that the tangential series of the one form of tissue are sometimes single, sometimes double or multiple, and are interrupted by interpolated elements of the other form; while the average width of the adjoining tissue-elements of the two

. Comparative anatomy of the vegetative organs of the phanerogams and ferns;. Plant anatomy; Ferns. SECONDARY THICKENING. NORMAL DICOTYLEDONS. 531 the cambium, remained for a long time extremely obscure, and the accurate repre- sentations given by Th. Hartig as early as 1837 failed to be understood, until Mohl, in 1855', brought them into deserved honour. For the same reasons later investi- gations often leave much to be desired, and the special anatomy of the bast is but insufBciently treated of by most authors. Sect. i6z. The main fundamental mass of the medullary rays always consists of par Stock Photo

RMRE2N91–. Comparative anatomy of the vegetative organs of the phanerogams and ferns;. Plant anatomy; Ferns. SECONDARY THICKENING. NORMAL DICOTYLEDONS. 531 the cambium, remained for a long time extremely obscure, and the accurate repre- sentations given by Th. Hartig as early as 1837 failed to be understood, until Mohl, in 1855', brought them into deserved honour. For the same reasons later investi- gations often leave much to be desired, and the special anatomy of the bast is but insufBciently treated of by most authors. Sect. i6z. The main fundamental mass of the medullary rays always consists of par

. The Annals and magazine of natural history; zoology, botany, and geology. Natural history; Zoology; Botany; Geology. LP I LAI. LAir dorsal ones; it would be certainly strange if the opposite took place with regard to the hinge, where the ventral part^ would be the older and the dorsal parts the younger ones— tiiat is to say, the hinge would grow just in the opposite direction to the remainder of the shell." This certainly would be strange, but Dr. Noettling overlooks three facts :— Firstly. That, as is shown by the growth-lines, the teeth are formed entirely by secondary thickening whic Stock Photo

RMRMN86C–. The Annals and magazine of natural history; zoology, botany, and geology. Natural history; Zoology; Botany; Geology. LP I LAI. LAir dorsal ones; it would be certainly strange if the opposite took place with regard to the hinge, where the ventral part^ would be the older and the dorsal parts the younger ones— tiiat is to say, the hinge would grow just in the opposite direction to the remainder of the shell." This certainly would be strange, but Dr. Noettling overlooks three facts :— Firstly. That, as is shown by the growth-lines, the teeth are formed entirely by secondary thickening whic

. Botany of the living plant. Botany. LYCOPODIALES 319 below for Ferns. It consists of sharply circumscribed stelar tracts, with tracheides but no vessels, and no secondary thickening. But the greatest interest lies not in the structure of the plant so much as in its sporangia, and the germination of its spores : for these give hnes of comparison with the Seed-Plants. The strobilus or cone that bears them is distal on a vegetative branch, and even in the flattened species it has the primitive radial form, all the sporophylls being of equal size (Fig. 259, A). A longitudinal section shows that Stock Photo

RMRDY7C5–. Botany of the living plant. Botany. LYCOPODIALES 319 below for Ferns. It consists of sharply circumscribed stelar tracts, with tracheides but no vessels, and no secondary thickening. But the greatest interest lies not in the structure of the plant so much as in its sporangia, and the germination of its spores : for these give hnes of comparison with the Seed-Plants. The strobilus or cone that bears them is distal on a vegetative branch, and even in the flattened species it has the primitive radial form, all the sporophylls being of equal size (Fig. 259, A). A longitudinal section shows that

$. Plant life, considered with special references to form and function. Plant physiology. Fir;. ,Sy.—Transverse section of two bundles from the peripherj' of the stele of root of broad bean (/ icia Faba) at the beginning of secon- dar' tliickening. The xylem bundle, ^, is shaded; the phloem bundle unshaded, z the stelar cambium; /, the pericycle, also showing tangential di'isions in parts ; s, the endoder- mis. Highly magnified.—After Haberlandt.. Fig. S9.—Transerse section of the stele of root of bean {Phascolus multiflortis) shortly after secondary thickening has begun. ,f, endodermis; pc Stock Photo$

RMRDYAKC–. Plant life, considered with special references to form and function. Plant physiology. Fir;. ,Sy.—Transverse section of two bundles from the peripherj' of the stele of root of broad bean (/ icia Faba) at the beginning of secon- dar' tliickening. The xylem bundle, ^, is shaded; the phloem bundle unshaded, z the stelar cambium; /, the pericycle, also showing tangential di'isions in parts ; s, the endoder- mis. Highly magnified.—After Haberlandt.. Fig. S9.—Transerse section of the stele of root of bean {Phascolus multiflortis) shortly after secondary thickening has begun. ,f, endodermis; pc

RMRDC7PT–. Studies in fossil botany . Paleobotany. 146 STUDIES IN FOSSIL BOTANY forms, the development of the xylem must have been centripetal. Immediately within the protoxylem the elements become much larger, forming a broad continu- ous zone, which consists exclusively of long scalariform tracheides, without any admixture of parenchyma (Figs.. "«:#, Fig. 60.—Lepidodendron selaginoides. Transverse section of stele after commencement of secondary thickening. .*:, primary xylem-cylinder, with reticulate tracheides in central part, and small protoxylem-elements at periphery ; jr2, secondary wood, u

. Botany of the living plant. Botany; Plants. 530 BOTANY OF THE LIVING PLANT There is no need to describe the minute structure of the vegetative organs, since it corresponds in essentials to what has been seen in Angiosperms. It must suffice to note certain features of comparative importance. The stem is constructed on the same plan as that of the woody Dicotyledons, with indefinite secondary thickening of the vascular ring originating from a cambium (compare Fig. 35, p. 57). It results in the Scots Pine in a woody trunk marked by annual rings and medullary rays, while externally are phloem an Stock Photo

RMRH8NNW–. Botany of the living plant. Botany; Plants. 530 BOTANY OF THE LIVING PLANT There is no need to describe the minute structure of the vegetative organs, since it corresponds in essentials to what has been seen in Angiosperms. It must suffice to note certain features of comparative importance. The stem is constructed on the same plan as that of the woody Dicotyledons, with indefinite secondary thickening of the vascular ring originating from a cambium (compare Fig. 35, p. 57). It results in the Scots Pine in a woody trunk marked by annual rings and medullary rays, while externally are phloem an

. Plant life, considered with special references to form and function. Plant physiology. THE STEM. "S concentric with the surface of the stem (figs. 120, 124, 133^-!). As its cells divide, sometimes their inner, sometimes their outer segments differentiate into the tissues which they then. sn^" Fig. 133.—Diagrams of transverse sections of stems illustrating modes of secondary thickening. In all f, cortex; cii. endoderniis ; /, pericycle ; //;', primary phloem ; J'lt' , secondary phloem; ch^ stelar caml.ium ; j^', primary xvlem ; j.", secondary xylem ; ?-', primary pith rays ; r& Stock Photo

RMRDYAAC–. Plant life, considered with special references to form and function. Plant physiology. THE STEM. "S concentric with the surface of the stem (figs. 120, 124, 133^-!). As its cells divide, sometimes their inner, sometimes their outer segments differentiate into the tissues which they then. sn^" Fig. 133.—Diagrams of transverse sections of stems illustrating modes of secondary thickening. In all f, cortex; cii. endoderniis ; /, pericycle ; //;', primary phloem ; J'lt' , secondary phloem; ch^ stelar caml.ium ; j^', primary xvlem ; j.", secondary xylem ; ?-', primary pith rays ; r&

. A textbook of botany for colleges and universities ... Botany. Fig. 641. — Enlarged details of spiral {$), pitted (p), and reticulate (r) tracheae; at i, traces of original partition walls. — Adapted from Haberlandt and TscHIRCH. ones. When numerous primary and secondary strands are produced, they may form a column of xylem, with pith in the center, interrupted by thin radiating plates of parenchyma, the. pith rays. Such is the condition in the sun- flower, castor bean (fig. 644), and many other dicotyledons. In case the xylem strands do not undergo individual secondary thickening (as is the Stock Photo

RMRDXT3R–. A textbook of botany for colleges and universities ... Botany. Fig. 641. — Enlarged details of spiral {$), pitted (p), and reticulate (r) tracheae; at i, traces of original partition walls. — Adapted from Haberlandt and TscHIRCH. ones. When numerous primary and secondary strands are produced, they may form a column of xylem, with pith in the center, interrupted by thin radiating plates of parenchyma, the. pith rays. Such is the condition in the sun- flower, castor bean (fig. 644), and many other dicotyledons. In case the xylem strands do not undergo individual secondary thickening (as is the

RMREFEGR–. Comparative anatomy of the vegetative organs of the phanerogams and ferns. Plant anatomy; Phanerogams; Ferns. SECONDARY THICKENING. NORMAL DICOTYLEDONS. 463 to this, even casual observation shows that the secondary growth on the side of the wood is almost always far more abundant than on the side of the bast. Both the successively developed elements of the wood and bast, and the cells of the initial layer, in certain cases, increase for a time in size, while growth in thickness proceeds, as will be described in greater detail below; from a definite period onwards, however, a constant average

RMRDFE5R–. Fossil plants : for students of botany and geology . Paleobotany. xxv] ANKYROPTERIS 459 sieve-tubes, Sv, and the flattened cells resemble tissues in a corresponding position in the steles of modern Osmundaceae. In a section of Ankyropteris corrugata in the Williamson Collection the radial arrangement of the more external meta- xylem elements suggests the addition of secondary tracheae'. This suggestion of secondary thickening, a point which requires much more thorough investigation, is interesting in relation to a new type of stem named by Scott Botrychioxylon^, but not yet fully described.

RMRDBCCY–. Fossil plants : for students of botany and geology . Paleobotany. X] ARTHROPITYS. 313 result of active growth, and not merely the expression of the tangential stretching of the stem consequent on secondary thickening. A glance at the complete transverse section of the stem,— of which a small portion is shown in fig. 74 A,—suggests the existence of annual rings in the wood, but this appearance of rings is merely the result of compression. The secondary wood of a Calamite does not exhibit any regular zones of growth comparable with the annual rings of our forest trees.. Fig. 75. Longitudinal t

. The Biological bulletin. Biology; Zoology; Marine biology. EYES OF CAMBARUS SETOSUS AND CAMBARUS PELLUCIDUS. 391 The part of the degenerated eye of the blind crayfish which is of chief interest is the retinal hypodermis. Here the largest amount of degeneration has taken place. The optic ganglion, optic tract and brain show little or no signs of degeneration. The condition of these structures is well illustrated by photo-. FiG. 7. A secondary thickening of the hypodermis from the antero-median part of an eye of C setosus. micrographs B, C and D. The optic nerves (Fig. 8 and photo- micrographs Stock Photo

RMRHG8EG–. The Biological bulletin. Biology; Zoology; Marine biology. EYES OF CAMBARUS SETOSUS AND CAMBARUS PELLUCIDUS. 391 The part of the degenerated eye of the blind crayfish which is of chief interest is the retinal hypodermis. Here the largest amount of degeneration has taken place. The optic ganglion, optic tract and brain show little or no signs of degeneration. The condition of these structures is well illustrated by photo-. FiG. 7. A secondary thickening of the hypodermis from the antero-median part of an eye of C setosus. micrographs B, C and D. The optic nerves (Fig. 8 and photo- micrographs

. An introduction to the structure and reproduction of plants. Plant anatomy; Plants. GENERAL FEATURES OF SECONDARY THICKENING 119 The secondary wood thus added on the inside forms a larger and larger core each year (Fig, 58). Since it is composed of hard persistent tissue, there is practically no compression of the wood, which progressively accumulates, so that the increase in girth of the stem serves as a rough measure of the amount of tissue added. To this enlargement the secondary phloem con-. FiG. 58.—Diagram showing the arrangement of tissues in a transverse section of a woody trunk abou Stock Photo

RMRDWRAR–. An introduction to the structure and reproduction of plants. Plant anatomy; Plants. GENERAL FEATURES OF SECONDARY THICKENING 119 The secondary wood thus added on the inside forms a larger and larger core each year (Fig, 58). Since it is composed of hard persistent tissue, there is practically no compression of the wood, which progressively accumulates, so that the increase in girth of the stem serves as a rough measure of the amount of tissue added. To this enlargement the secondary phloem con-. FiG. 58.—Diagram showing the arrangement of tissues in a transverse section of a woody trunk abou

. Comparative anatomy of the vegetative organs of the phanerogams and ferns;. Plant anatomy; Ferns. 258 PRIMARY ARRANGEMENT OF TISSUES. > In the internode of Nef^nties' there is fouSd an inner typical bundle-ring, surrounding the pith, which later undergoes secondary thickening, and externally other bundles are. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work.. Bary, A. de (Anton), 1831-1888; Bower, F. O. (Frederick Orpen) Stock Photo

RMRE3CEX–. Comparative anatomy of the vegetative organs of the phanerogams and ferns;. Plant anatomy; Ferns. 258 PRIMARY ARRANGEMENT OF TISSUES. > In the internode of Nef^nties' there is fouSd an inner typical bundle-ring, surrounding the pith, which later undergoes secondary thickening, and externally other bundles are. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work.. Bary, A. de (Anton), 1831-1888; Bower, F. O. (Frederick Orpen)

. Botany of the living plant. Botany. Young leaf of Ccratopteris, in surface iev, after Kuy: showing two-sided apical ceil ; and the marginal series, continuous round the young pinnae. Tlie latter do not correspond to the segments from the apical cell. Thus constituted the Fern- Plant carries out its life on Land in essentially the same way as Seed-Plants. The struc- tural differences are those of detail, the most important being the absence of secondary thickening in the stem. These plants have no automatic provision for increasing mechanical strength with size. In Tree-Ferns this deficienc Stock Photo

RMRDY76N–. Botany of the living plant. Botany. Young leaf of Ccratopteris, in surface iev, after Kuy: showing two-sided apical ceil ; and the marginal series, continuous round the young pinnae. Tlie latter do not correspond to the segments from the apical cell. Thus constituted the Fern- Plant carries out its life on Land in essentially the same way as Seed-Plants. The struc- tural differences are those of detail, the most important being the absence of secondary thickening in the stem. These plants have no automatic provision for increasing mechanical strength with size. In Tree-Ferns this deficienc

. A textbook of botany for colleges and universities ... Botany. pith rays. Such is the condition in the sun- flower, castor bean (fig. 644), and many other dicotyledons. In case the xylem strands do not undergo individual secondary thickening (as is the case in most monocoty- ledons), there may be a cylinder of meristem which repeatedly produces new bundles, as in asparagus. But in all plants which produce numerous leaves the increasing evaporation is Fig. 642. — Young vas- cular bundle: p, primary phloem ; x^ primary xylem ; c, iirst divisions of cambium cells.—After Bonnier. Diagrammatic.. Stock Photo

RMRDXT3J–. A textbook of botany for colleges and universities ... Botany. pith rays. Such is the condition in the sun- flower, castor bean (fig. 644), and many other dicotyledons. In case the xylem strands do not undergo individual secondary thickening (as is the case in most monocoty- ledons), there may be a cylinder of meristem which repeatedly produces new bundles, as in asparagus. But in all plants which produce numerous leaves the increasing evaporation is Fig. 642. — Young vas- cular bundle: p, primary phloem ; x^ primary xylem ; c, iirst divisions of cambium cells.—After Bonnier. Diagrammatic..

. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. ANATOMY 461 the stem of the young plant, but fades off in the upper regions, as in Ophioglossum. In transverse sections of the stock of Botrychium, in which the leaf- gaps are limited in area and not so closely placed as in Ophioglossum, the vascular ring is often seen to be complete, or where a leaf-trace issues it may be interrupted : the xylem is endarch. Much importance has been accorded to the secondary thickening seen in both stem and root of Botrychium. A sluggish cambium appears between the ph Stock Photo

RMRDXF9N–. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. ANATOMY 461 the stem of the young plant, but fades off in the upper regions, as in Ophioglossum. In transverse sections of the stock of Botrychium, in which the leaf- gaps are limited in area and not so closely placed as in Ophioglossum, the vascular ring is often seen to be complete, or where a leaf-trace issues it may be interrupted : the xylem is endarch. Much importance has been accorded to the secondary thickening seen in both stem and root of Botrychium. A sluggish cambium appears between the ph

. Botany of the living plant. Botany. THE TISSUES OF THE STEM 49 cells will appear long and narrow, with square ends (Fig. 24). Putting together the results of these three sections, the form of the cell as a solid body would be flattened prismatic ; it is placed with. Fig. 36. Diagrams of secondary thickening in stem of Dicotyledon, based on transverse sections of the hypocotyl of Ricinus. A represents the stem before origin of inter- fascicular cambium. B, same after it has been formed. C, after it has produced internally a broad ring of secondary wood, and externally a narrower ring of secon Stock Photo

RMRH92G3–. Botany of the living plant. Botany. THE TISSUES OF THE STEM 49 cells will appear long and narrow, with square ends (Fig. 24). Putting together the results of these three sections, the form of the cell as a solid body would be flattened prismatic ; it is placed with. Fig. 36. Diagrams of secondary thickening in stem of Dicotyledon, based on transverse sections of the hypocotyl of Ricinus. A represents the stem before origin of inter- fascicular cambium. B, same after it has been formed. C, after it has produced internally a broad ring of secondary wood, and externally a narrower ring of secon

. Plant anatomy from the standpoint of the development and functions of the tissues, and handbook of micro-technic. Plant anatomy. UNUSUAL GROWTH IN THICKNESS 59 Some of the climbing Big- noniaceae vary from the usual type by the cambium failing to form xylem here and there as secondary thickening progresses; so that the wood cylinder becomes more or less deeply cleft by the phloem (Fig. 30, A). In extreme instances the wood may become cut up into many isolated strands by the production of secondary meristems from cell division in the wood parenchyma, medullary rays and pith (Fig. 30, B), and Stock Photo

RMRE2ENT–. Plant anatomy from the standpoint of the development and functions of the tissues, and handbook of micro-technic. Plant anatomy. UNUSUAL GROWTH IN THICKNESS 59 Some of the climbing Big- noniaceae vary from the usual type by the cambium failing to form xylem here and there as secondary thickening progresses; so that the wood cylinder becomes more or less deeply cleft by the phloem (Fig. 30, A). In extreme instances the wood may become cut up into many isolated strands by the production of secondary meristems from cell division in the wood parenchyma, medullary rays and pith (Fig. 30, B), and

. Botany of the living plant. Botany. THE TISSUES OF THE STEM 49 cells will appear long and narrow, with square end:^ (Fig. 24). Putting together the results of these three sections, the form of the cell as a solid body would be flattened prismatic ; it is placed with. Fig. 36. Diagianis of secondary thickening in stem of Dicotyledon, based on transverse sections of the hypocotyl of Ricinus. A represents the stem before origin of inter- fascicular cambiam. B, same after it has been formed. C, after it has produced internally a broad ring of secondary wood, and externally a narrower ring of sec Stock Photo

RMRDY9CP–. Botany of the living plant. Botany. THE TISSUES OF THE STEM 49 cells will appear long and narrow, with square end:^ (Fig. 24). Putting together the results of these three sections, the form of the cell as a solid body would be flattened prismatic ; it is placed with. Fig. 36. Diagianis of secondary thickening in stem of Dicotyledon, based on transverse sections of the hypocotyl of Ricinus. A represents the stem before origin of inter- fascicular cambiam. B, same after it has been formed. C, after it has produced internally a broad ring of secondary wood, and externally a narrower ring of sec

. An introduction to the structure and reproduction of plants. Plant anatomy; Plants. ANOMALOUS TYPES OF SECONDARY THICKENING 133 In many members of the Spinach-family (Chenopodiaccit) the normal cambium functions only for a short time and, after forming a narrow strip of secondary xylem and phloem, ceases to divide. Thereupon another cambium arises in the inner part of the cortex, and a new strip of xylem and phloem is produced till this cambium in its turn ceases to be active. This process is repeated again and again, each successive cam- bium forming xjdem on the inner and phloem on the out Stock Photo

RMRDWR8P–. An introduction to the structure and reproduction of plants. Plant anatomy; Plants. ANOMALOUS TYPES OF SECONDARY THICKENING 133 In many members of the Spinach-family (Chenopodiaccit) the normal cambium functions only for a short time and, after forming a narrow strip of secondary xylem and phloem, ceases to divide. Thereupon another cambium arises in the inner part of the cortex, and a new strip of xylem and phloem is produced till this cambium in its turn ceases to be active. This process is repeated again and again, each successive cam- bium forming xjdem on the inner and phloem on the out

. An introduction to the structure and reproduction of plants. Plant anatomy; Plants. SECONDARY THICKENING OF ROOTS 131 A transverse section of any unthickened Dicotyledonous root will show a narrow band of two or three laj'ers of parench^-matous cells between each phloem-group and the adjacent xylem. Prior to the commencement of secondar}- growth tangential division- walls arise in these cells, leading to the production of a cambium (Fig. 27, ca.,p. 66) like that of the stem. In this way there originate as many cambial strips (Fig. 63, A, B, C.) as there are groups of phloem, and, by the acti Stock Photo

RMRDWR9B–. An introduction to the structure and reproduction of plants. Plant anatomy; Plants. SECONDARY THICKENING OF ROOTS 131 A transverse section of any unthickened Dicotyledonous root will show a narrow band of two or three laj'ers of parench^-matous cells between each phloem-group and the adjacent xylem. Prior to the commencement of secondar}- growth tangential division- walls arise in these cells, leading to the production of a cambium (Fig. 27, ca.,p. 66) like that of the stem. In this way there originate as many cambial strips (Fig. 63, A, B, C.) as there are groups of phloem, and, by the acti

RMRDC84W–. Studies in fossil botany . Paleobotany. 22 STUDIES IN FOSSIL BOTANY preserved at the very commencement, or even before the commencement, of secondary growth, as shown in Fig. 5. This is a comparatively rare stage to find, and when it is found, it is nearly always in a small twig. The larger stems of Catamites are rarely, if ever, met with at so early a stage of development. In a twig in this early condition, before secondary thickening has begun, the pith is often persistent (though fistular in the specimen figured), and round it we find a ring of. Fig. 5.—Calaviites, sp. Transverse section

. Botany of the living plant. Botany. Fig. 275. Young leaf of Ceratopteris, in surface view, after Kuy; showing two-sided apical cell; and the marginal series, continuous round the young pinnae. The latter do not correspond to the segments from the apical cell. Thus constituted the Fern- Plant carries out its life on Land in essentially the same way as Seed-Plants. The struc- tural differences are those of detail, the most important being the absence of secondary thickening in the stem. These plants have no automatic provision for increasing mechanical strength with size. In Tree-Ferns this de Stock Photo

RMRH8TX0–. Botany of the living plant. Botany. Fig. 275. Young leaf of Ceratopteris, in surface view, after Kuy; showing two-sided apical cell; and the marginal series, continuous round the young pinnae. The latter do not correspond to the segments from the apical cell. Thus constituted the Fern- Plant carries out its life on Land in essentially the same way as Seed-Plants. The struc- tural differences are those of detail, the most important being the absence of secondary thickening in the stem. These plants have no automatic provision for increasing mechanical strength with size. In Tree-Ferns this de

. Botany for secondary schools; a guide to the knowledge of the vegetation of the neighborhood. Plants. 292 STRUCTURE OF STEMS AND ROOTS ring itself to enlarge its circumference and to move out- ward by this growth. 496. To study secondary thickening: Cut thin cross- sections of basswood stems of different ages (one to three years old). Stain and mount. Examine with low power and. 462. Microphotograph of cross-section showing secondary growth in larch, June 13; a, cambium; a-b, new phloem; a-c, new wood. D. Tagential section of wood of pine, showing transverse section of medullary rays; rd, tr Stock Photo

RMRH4W30–. Botany for secondary schools; a guide to the knowledge of the vegetation of the neighborhood. Plants. 292 STRUCTURE OF STEMS AND ROOTS ring itself to enlarge its circumference and to move out- ward by this growth. 496. To study secondary thickening: Cut thin cross- sections of basswood stems of different ages (one to three years old). Stain and mount. Examine with low power and. 462. Microphotograph of cross-section showing secondary growth in larch, June 13; a, cambium; a-b, new phloem; a-c, new wood. D. Tagential section of wood of pine, showing transverse section of medullary rays; rd, tr

. Plants and their ways in South Africa. Botany; Botany. Stem and Root Stnictuir^s 77 each bundle is surrounded by a fibrous sheath developed from the ground tissue.. Fig. 74.—P.irt of a transverse section through the stem of Tradescaniia St'//i>i': ('. epidermis, ith a sioma, s/; R, cortex ; V, thickening ring with the outer vascular bundles, g' ; j;^", mner vascular bundles ( x 75). Secondary Thickening in Monocotyledons.—Since the closed bundles of monocotyledons allow for no secondary thickening, the structure of the mature stem resembles that of. Please note that these images ar Stock Photo

RMRDWE4C–. Plants and their ways in South Africa. Botany; Botany. Stem and Root Stnictuir^s 77 each bundle is surrounded by a fibrous sheath developed from the ground tissue.. Fig. 74.—P.irt of a transverse section through the stem of Tradescaniia St'//i>i': ('. epidermis, ith a sioma, s/; R, cortex ; V, thickening ring with the outer vascular bundles, g' ; j;^", mner vascular bundles ( x 75). Secondary Thickening in Monocotyledons.—Since the closed bundles of monocotyledons allow for no secondary thickening, the structure of the mature stem resembles that of. Please note that these images ar

. Plants and their ways in South Africa. Botany; Botany. 82 Plants and their Ways in South Africa activity is first evident. Once the ring is formed it lays down wood to the inside, phloem to the outside, with medullary rays at intervals, much as secondary thickening takes place in a stem. When cork is formed, it also takes its rise in the pericycle.. Fig. 78.âCross section of bean root, diagrammatic, a. Primary corte.x', with outer piliferous layer, and inner endodermis ; /', pericycle ; <-, primary xylem ; t/, primary phloem ; e, a ruig of cambium formed of ground tissue between the phloe Stock Photo

RMRDWE3X–. Plants and their ways in South Africa. Botany; Botany. 82 Plants and their Ways in South Africa activity is first evident. Once the ring is formed it lays down wood to the inside, phloem to the outside, with medullary rays at intervals, much as secondary thickening takes place in a stem. When cork is formed, it also takes its rise in the pericycle.. Fig. 78.âCross section of bean root, diagrammatic, a. Primary corte.x', with outer piliferous layer, and inner endodermis ; /', pericycle ; <-, primary xylem ; t/, primary phloem ; e, a ruig of cambium formed of ground tissue between the phloe

. Elements of plant biology. Plant physiology. 336 THE WOODY STEM. PriTuaLTy xylcnv Fig. 55.—Diagrams of secondary thickening in the stem. A, cross- section of stem with bundles separated by broad primary rays in the first year of thickening; secondary xylem and phloem are formed all round the cylinder, bridging the broad primary rays. B, ditto, with bundles separated by narrow primary rays; the cambium continues the primary rays as secondary (principal) rays; s.t., secondary tissue. C, section of stem after six years of thickening; the primary rays are continued as principal rays, and new nar Stock Photo

RMRDHNKH–. Elements of plant biology. Plant physiology. 336 THE WOODY STEM. PriTuaLTy xylcnv Fig. 55.—Diagrams of secondary thickening in the stem. A, cross- section of stem with bundles separated by broad primary rays in the first year of thickening; secondary xylem and phloem are formed all round the cylinder, bridging the broad primary rays. B, ditto, with bundles separated by narrow primary rays; the cambium continues the primary rays as secondary (principal) rays; s.t., secondary tissue. C, section of stem after six years of thickening; the primary rays are continued as principal rays, and new nar

. Plant life, considered with special references to form and function. Plant physiology. THE ROOT. 77 and the phloem region, nith the cortex between them, if anything is left of it, constitute a I/ark, which becomes fur- rowed lengthwise, like the bark of the stems of many trees. Such secondary thickening finally produces in the roots a. Fig. qi.âA. diagram of priman' structure. P. C. diagrams shon-ing the results of secondare' thickeniug from the stclar cambium in the two extreme forms c. cortex; e^i. dudodermis : /-, pericycle ; /-h'. primary phloem ; /A", secondary phloem ; .r'* primar Stock Photo

RMRDYAJ5–. Plant life, considered with special references to form and function. Plant physiology. THE ROOT. 77 and the phloem region, nith the cortex between them, if anything is left of it, constitute a I/ark, which becomes fur- rowed lengthwise, like the bark of the stems of many trees. Such secondary thickening finally produces in the roots a. Fig. qi.âA. diagram of priman' structure. P. C. diagrams shon-ing the results of secondare' thickeniug from the stclar cambium in the two extreme forms c. cortex; e^i. dudodermis : /-, pericycle ; /-h'. primary phloem ; /A", secondary phloem ; .r'* primar

RMRDBCMP–. Studies in fossil botany . Paleobotany. STIGMARIA 255 however, we find an addition of radially arranged secondary wood (see Fig. 104, 3?), and where this is the case the secondary formation is always limited to the side remote from the protoxylem, thus affording yet another indication of monarch structure. The formation of secondary wood, though rare in the free rootlets, is. JOX. DC Fig. 104.—Stigmaria ficoides. Transverse section o central part of rootlet, to show secondary thickening of wood, jr, primary xylem ; px, protoxylem ; -r2, secondary xylem, limited to one side of bundle ; i.c, i

RMRDC84N–. Studies in fossil botany . Paleobotany. THE STEM OF CALAMITES 25 far as anatomy goes, is simply an Equisetum with secondary thickening. In order to carry the comparison further, we must settle one or two points, especially the course of the vascular bundles. In Equisetum itself their course is exceedingly simple: a single vascular bundle enters the stem from each leaf, and. Fig. 7.—Calamitcs, sp. Radial section of a decorticated stem, with fairly thick wood, showing the fistular pith, crossed by diaphragms at the nodes. X 9. From a photo- graph. Phil. Trans., W. and S. Will. Coll. 1937. pass

RMRDBC98–. Fossil plants : for students of botany and geology . Paleobotany. Fig. 91. A. Diagrammatic sketch of a transverse section of a young root of Galamites. x, xylem; I, lacuna. After Hick. B. Central cylinder (stele) of root, px, protoxylem; ph, phloem; x^, secondary xylem; I, phloeoterma. x 75. After Williamson and Scott. the figure secondary thickening has begun, and the cambial cells internal to each phloem group have given rise to a few radially disposed tracheids, x Beyond the phloem there are two layers of parenchyma representing, as regards position, a pericycle and an endodermis. In the

RMRDBCAP–. Fossil plants : for students of botany and geology . Paleobotany. ABC Pig. 140. Picea excelsa. Shoots of different ages showing changes in the appear- ance of the leaf-cushions: a leaf attached to a cushion in fig. A. (Slightly enlarged.) A portion of the cushion below the triangular leaf-scar often shows transverse gaping cracks or depressions (fig. 185, C) such as occur on a smaller scale on the older cushions of a Fir twig (fig. 140). Secondary thickening, as in recent trees, is not confined to the vascular cylinder but at an early stage, frequently before there are any signs of secondary

. A manual of botany. Botany. Fig. 743. Diagi-am of stem of Dicotyledon at three ages. a. Young condi- tion showing commencement of differentiation of the stele and its fibro- vascular bundles, a. Procambium bundles arising in 6, the stele, c. Cortex, 771.7". Medullary ray. pi. Pith. b. A little older stage, p. Phloem, X. Xylem. c. Fascicular cambium, i.e. Interfascicular cambium. One of the bundles has been shaded, c, Older stage after the commencement of secondary thickening, ^^a;. Protoxylem. .r. Secondary wood. p7i. Secon- dary bast. a. Kew bundles formed by the interfascicular cambiu Stock Photo

RMRE1J3C–. A manual of botany. Botany. Fig. 743. Diagi-am of stem of Dicotyledon at three ages. a. Young condi- tion showing commencement of differentiation of the stele and its fibro- vascular bundles, a. Procambium bundles arising in 6, the stele, c. Cortex, 771.7". Medullary ray. pi. Pith. b. A little older stage, p. Phloem, X. Xylem. c. Fascicular cambium, i.e. Interfascicular cambium. One of the bundles has been shaded, c, Older stage after the commencement of secondary thickening, ^^a;. Protoxylem. .r. Secondary wood. p7i. Secon- dary bast. a. Kew bundles formed by the interfascicular cambiu

. Botany of the living plant. Botany; Plants. Fig. 37. Diagrams of secondary thickening in stem of Dicotyledon, based on transverse sections of the hypocotyl of Ricinus. A represents the stem before origin of inter- fascicular cambium. B, same after it has been formed. C, after it has produced internally a broad ring of secondary wood, and externally a narrower ring of secon- dary phloem. 2? = primary cortex. M=pith. £=phloem. #=primary xylem. 6 = bast fibres at periphery of phloem, fc = fascicular cambium. ic = interfascicular cambium, fh = wood of primary bundle. i/fe = wood developed from i Stock Photo

RMRH8GMD–. Botany of the living plant. Botany; Plants. Fig. 37. Diagrams of secondary thickening in stem of Dicotyledon, based on transverse sections of the hypocotyl of Ricinus. A represents the stem before origin of inter- fascicular cambium. B, same after it has been formed. C, after it has produced internally a broad ring of secondary wood, and externally a narrower ring of secon- dary phloem. 2? = primary cortex. M=pith. £=phloem. #=primary xylem. 6 = bast fibres at periphery of phloem, fc = fascicular cambium. ic = interfascicular cambium, fh = wood of primary bundle. i/fe = wood developed from i

. Botany of the living plant. Botany; Plants. phl"-.- V pr.pld --^pp.phl. pr.xy p.mr pr.xg Fig. 67. Diagram A shows arrangement of tissues in a young root of a Dicotyledon before cambial activity begins. B. the same when cambium can be clearly recognised. C. after secondary thickening has progressed. c=cortex, present in A and B, but in C it has been thrown off. pr.phl=primary phloem. />/;/"=secondary phloem. pr.xy=primary xylem. .vy"=secondary xylem. £.wr=primary medullary ray. mr" =secondary medullary ray. ;/i=pith. F.O.B. Compare Fig. 37, p. 58. the ground, while evi Stock Photo

RMRH8G16–. Botany of the living plant. Botany; Plants. phl"-.- V pr.pld --^pp.phl. pr.xy p.mr pr.xg Fig. 67. Diagram A shows arrangement of tissues in a young root of a Dicotyledon before cambial activity begins. B. the same when cambium can be clearly recognised. C. after secondary thickening has progressed. c=cortex, present in A and B, but in C it has been thrown off. pr.phl=primary phloem. />/;/"=secondary phloem. pr.xy=primary xylem. .vy"=secondary xylem. £.wr=primary medullary ray. mr" =secondary medullary ray. ;/i=pith. F.O.B. Compare Fig. 37, p. 58. the ground, while evi

. Botany, an elementary text for schools. Botany. SECONDARY THICKEXTXC OF STK^fS I'l;.". P c Prepare cross-sections of the sti-m df ptrris or asitidium. They should be cut verj' tliiii and staiii<nt one 4(i4. I â ., â¢ ' ' (I - v;is- fuliii-liiuiiUu oi iiiiH.u.siiil ^set> Imnille. Fig. 402). f, f, cnsi-.-iit-sliaiM-d sheiitl.sofbasttil,re;;y,l.l.lo.-ni; 42s. SECONDARY THICKENING OP^ c;i, cnishfd lililoi-m ; c, ciim- i.ium; d.xjlomaiicts; ^.i 1.1.1 STEMS.â 1 )ic()t k'doMous (or io- tnii-liciils; 111, iiicdiillary rajs of fui..la.noiital tissu..; from cr,.n,,us) stcMlS witil OpCM Stock Photo

RMRH8XXJ–. Botany, an elementary text for schools. Botany. SECONDARY THICKEXTXC OF STK^fS I'l;.". P c Prepare cross-sections of the sti-m df ptrris or asitidium. They should be cut verj' tliiii and staiii<nt one 4(i4. I â ., â¢ ' ' (I - v;is- fuliii-liiuiiUu oi iiiiH.u.siiil ^set> Imnille. Fig. 402). f, f, cnsi-.-iit-sliaiM-d sheiitl.sofbasttil,re;;y,l.l.lo.-ni; 42s. SECONDARY THICKENING OP^ c;i, cnishfd lililoi-m ; c, ciim- i.ium; d.xjlomaiicts; ^.i 1.1.1 STEMS.â 1 )ic()t k'doMous (or io- tnii-liciils; 111, iiicdiillary rajs of fui..la.noiital tissu..; from cr,.n,,us) stcMlS witil OpCM

Organic and functional nervous diseases; a text-book of neurology . t cases, Putnam being the only observer to distinguish betweensymptoms of long and of short standing in the same case. In addition to the sclerosis of the cord the majority of observers havenoticed a thickening of the pia mater, especially upon the posterior andlateral surfaces, with adhesion to the cord. Some have seen a state ofarterio-capillary fibrosis or a true endarteritis in the spinal vessels.The anterior nerve roots have been found atrophied. The combination of secondary degeneration of the motor and sensorytracts som Stock Photo

RM2AN24PJ–Organic and functional nervous diseases; a text-book of neurology . t cases, Putnam being the only observer to distinguish betweensymptoms of long and of short standing in the same case. In addition to the sclerosis of the cord the majority of observers havenoticed a thickening of the pia mater, especially upon the posterior andlateral surfaces, with adhesion to the cord. Some have seen a state ofarterio-capillary fibrosis or a true endarteritis in the spinal vessels.The anterior nerve roots have been found atrophied. The combination of secondary degeneration of the motor and sensorytracts som

A manual of diseases of the throat and nose : including the pharynx, larynx, trachea, oesophagus, nose and naso-pharynx . Fig. 67.—Condyloma on the Fig. 68.—Thickening and TJ1- TJpper Surface of the Epiglottis. ceration of the Epiglottis. tion, under the name of relapsing ulcerative laryngitis. When thesesuperficial ulcers occur within a year of the primary affection, I have beenin the habit of classifying them under the head of secondary syphilis,,though this is a mere arbitrary distinction. But when they appear threeor four years after inoculation, they may fairly be regarded as tertiary.I h Stock Photo

RM2AKANEH–A manual of diseases of the throat and nose : including the pharynx, larynx, trachea, oesophagus, nose and naso-pharynx . Fig. 67.—Condyloma on the Fig. 68.—Thickening and TJ1- TJpper Surface of the Epiglottis. ceration of the Epiglottis. tion, under the name of relapsing ulcerative laryngitis. When thesesuperficial ulcers occur within a year of the primary affection, I have beenin the habit of classifying them under the head of secondary syphilis,,though this is a mere arbitrary distinction. But when they appear threeor four years after inoculation, they may fairly be regarded as tertiary.I h

The signs of internal disease, with a brief consideration of the principal symptoms thereof . Fig- 37—Extension of tuberculous lesion (Patton).^ Dark shade—primary le-sion; light shade—extension of primary lesion; X—secondary lesion of op-posite apex. most apparent anteriorly and the breathing excursion is lessened bothwith quiet breathing and during forced inspiration, when lack ofexpansion is striking. Expansile efforts may be painful. 150 PULMONARY TUBERCULOSIS OR CONSUMPTION Palpation shows increased fremitus except, as noted in first stage,where pleurisy has resulted in thickening. The sk Stock Photo

RM2AN72HN–The signs of internal disease, with a brief consideration of the principal symptoms thereof . Fig- 37—Extension of tuberculous lesion (Patton).^ Dark shade—primary le-sion; light shade—extension of primary lesion; X—secondary lesion of op-posite apex. most apparent anteriorly and the breathing excursion is lessened bothwith quiet breathing and during forced inspiration, when lack ofexpansion is striking. Expansile efforts may be painful. 150 PULMONARY TUBERCULOSIS OR CONSUMPTION Palpation shows increased fremitus except, as noted in first stage,where pleurisy has resulted in thickening. The sk

Structural geology . layers contrasted in jasper. The broken darklayers are chert, the li^ht layers are secondary iron oxide. Folds may be formed by means of minute displacements alongnumerous joints and faults. Folds in brittle quartzite beds arecommonly of this type. There is no interior deformation of the fault and joint blocks,and there is no thickening or thinning of the beds as a whole. Thetop and bottom of a bed are parallel throughout. The fold is ofthe parallel type. The curvature of the beds so folded is not FOLDS OF FRACTURE AND FLOW CONTRASTED 109 the same through any considerable Stock Photo

RM2AWEKH9–Structural geology . layers contrasted in jasper. The broken darklayers are chert, the li^ht layers are secondary iron oxide. Folds may be formed by means of minute displacements alongnumerous joints and faults. Folds in brittle quartzite beds arecommonly of this type. There is no interior deformation of the fault and joint blocks,and there is no thickening or thinning of the beds as a whole. Thetop and bottom of a bed are parallel throughout. The fold is ofthe parallel type. The curvature of the beds so folded is not FOLDS OF FRACTURE AND FLOW CONTRASTED 109 the same through any considerable

Plastic surgery; its principles and practice . ss of the skin over the injected area.Redness of the skin over the injected area.Secondary diftusion of the injected mass. Hyperplasia of the connective tissue following the organizationof the injected matter. 16 1718 19 20 46 PLASTIC SURGERY 21. A yellow appearance and thickening of the skin after organiza-tion of the injected mass. 22. The breaking down of tissue and a resulting abscess due to thepressure of the injected mass upon the adjacent tissue after the injectionhas become organized. Some authors say that the injected paraffin is encapsul Stock Photo

RM2AJE3NA–Plastic surgery; its principles and practice . ss of the skin over the injected area.Redness of the skin over the injected area.Secondary diftusion of the injected mass. Hyperplasia of the connective tissue following the organizationof the injected matter. 16 1718 19 20 46 PLASTIC SURGERY 21. A yellow appearance and thickening of the skin after organiza-tion of the injected mass. 22. The breaking down of tissue and a resulting abscess due to thepressure of the injected mass upon the adjacent tissue after the injectionhas become organized. Some authors say that the injected paraffin is encapsul

A system of obstetrics . c I A, Horizontal Section through Secondary Optic Vesicle; B, cross-section through the same: C,vertical section passing through the choroidal fissure : vh, cavity of secondary optic vesicle :the mesoblast extends into it and forms later the vitreous humor; /, choroidal fissure; h,superficial epiblast; x, its thickening over the surface of the optic vesicle; I, portion ofthickened external epiblast which has been separated to form the lens, which latter is stilla hollow vesicle ; 8, inner, $, outer layer of optic cup. is represented at A, a vertical transverse section Stock Photo

RM2AWKHD6–A system of obstetrics . c I A, Horizontal Section through Secondary Optic Vesicle; B, cross-section through the same: C,vertical section passing through the choroidal fissure : vh, cavity of secondary optic vesicle :the mesoblast extends into it and forms later the vitreous humor; /, choroidal fissure; h,superficial epiblast; x, its thickening over the surface of the optic vesicle; I, portion ofthickened external epiblast which has been separated to form the lens, which latter is stilla hollow vesicle ; 8, inner, $, outer layer of optic cup. is represented at A, a vertical transverse section

Treatise on gynaecology : medical and surgical . e germinal epithelium coveringthe surface of the ovary. These tubes of Pfliiger are destined later todivide and diminish in order to produce the Grraalian follicles whichare a product of secondary evolution. PATHOLOGICAL AN^ATOMY OF OVAEIAN CYSTS. 93 (I have borrowed from De Sinety the following items of informa-tion regarding germinating epithelium, primordial ovules and Pflligerstubes. In the early stages of embryonic life, about the fourth day of in-cubation in a chick, a slight thickening of the epithelium is seen inthe anterior portion of t Stock Photo

RM2ANDG3X–Treatise on gynaecology : medical and surgical . e germinal epithelium coveringthe surface of the ovary. These tubes of Pfliiger are destined later todivide and diminish in order to produce the Grraalian follicles whichare a product of secondary evolution. PATHOLOGICAL AN^ATOMY OF OVAEIAN CYSTS. 93 (I have borrowed from De Sinety the following items of informa-tion regarding germinating epithelium, primordial ovules and Pflligerstubes. In the early stages of embryonic life, about the fourth day of in-cubation in a chick, a slight thickening of the epithelium is seen inthe anterior portion of t

Manual of pathological anatomy . iilP«. fei » ?«#* liiii From a case of secondary deposit in knee-joint, the same as described in the text in the next page.c, A cartilage cell, immensely hypertrophied, lying- in fibrous stuff, b, A villous pro-cess springing- from the synovial membrane, a, A strip of fibrous tissue containingthree enlarged cartilage cells—one is also figured separately. secretion of fluid, but does not in general terminate in the effusion 808 DISEASES OF THE JOINTS. of coagulable lymph, or in thickening: of the inflamed membrane.Fibrinous matter is, however, if the disease con Stock Photo

RM2AM6W3E–Manual of pathological anatomy . iilP«. fei » ?«#* liiii From a case of secondary deposit in knee-joint, the same as described in the text in the next page.c, A cartilage cell, immensely hypertrophied, lying- in fibrous stuff, b, A villous pro-cess springing- from the synovial membrane, a, A strip of fibrous tissue containingthree enlarged cartilage cells—one is also figured separately. secretion of fluid, but does not in general terminate in the effusion 808 DISEASES OF THE JOINTS. of coagulable lymph, or in thickening: of the inflamed membrane.Fibrinous matter is, however, if the disease con

. Interpretation of dental & maxillary roentgenograms . Fig. 106. Fig. 107. Fig. 106.—The partition of bone between the second molar and the maxillarysinus has been destroyed by periapical disease, producing a dirert communication ofthis tooth with the maxillary sinus and secondary infection of that cavity. Thesecond premolar, although containing a partial root Idling, and presenting someperiapical thickening, is separated from the antrum by a bony partition. The apicesof the canine and first premolar show nothing abnormal, but lie very close to the floorof the sinus. Fig. 107.—Second premolar Stock Photo

RM2CRM8AP–. Interpretation of dental & maxillary roentgenograms . Fig. 106. Fig. 107. Fig. 106.—The partition of bone between the second molar and the maxillarysinus has been destroyed by periapical disease, producing a dirert communication ofthis tooth with the maxillary sinus and secondary infection of that cavity. Thesecond premolar, although containing a partial root Idling, and presenting someperiapical thickening, is separated from the antrum by a bony partition. The apicesof the canine and first premolar show nothing abnormal, but lie very close to the floorof the sinus. Fig. 107.—Second premolar

. Interpretation of dental and maxillary roentgenograms . Fig. 106. Fig. 107. Fig. 106.—The partition of bone between the second molar and the maxillarysinus has been destroyed by periapical dsease, producing; a direct communication ofthis tooth with the maxillary sinus and secondary infection of that cavity. Thesecond premolar, although containing a partal root rtUing, and presenting someperiapical thickening, is separated from the antrum by a bony partition. The apicesof the canine and first premolar show nothing abnormal, but lie very close to the floorof the sinus. Fig. 107.—Second premo Stock Photo

RM2CRJX1K–. Interpretation of dental and maxillary roentgenograms . Fig. 106. Fig. 107. Fig. 106.—The partition of bone between the second molar and the maxillarysinus has been destroyed by periapical dsease, producing; a direct communication ofthis tooth with the maxillary sinus and secondary infection of that cavity. Thesecond premolar, although containing a partal root rtUing, and presenting someperiapical thickening, is separated from the antrum by a bony partition. The apicesof the canine and first premolar show nothing abnormal, but lie very close to the floorof the sinus. Fig. 107.—Second premo

RM2CRJWYT–. Interpretation of dental and maxillary roentgenograms . Fig. 106. Fig. 107. Fig. 106.—The partition of bone between the second molar and the maxillarysinus has been destroyed by periapical dsease, producing; a direct communication ofthis tooth with the maxillary sinus and secondary infection of that cavity. Thesecond premolar, although containing a partal root rtUing, and presenting someperiapical thickening, is separated from the antrum by a bony partition. The apicesof the canine and first premolar show nothing abnormal, but lie very close to the floorof the sinus. Fig. 107.—Second premo

. The American journal of roentgenology, radium therapy and nuclear medicine . Repeated enemata givenon different days show this appearance tobe constant. The serrations do not change in size orshape. Furthermore, palpation under the flu-oroscopic screen usually shows us that theintestine is more or less like a rigid tube.The walls are thickened and have lost theirnormal flexibility. One infers that the serrated appearanceis due to inflanmiatory thickening and in-duration in and about the intestinal wall,secondary to the presence of diverticula. Thediverticula themselves not being visible, per Stock Photo

RM2CRP3CE–. The American journal of roentgenology, radium therapy and nuclear medicine . Repeated enemata givenon different days show this appearance tobe constant. The serrations do not change in size orshape. Furthermore, palpation under the flu-oroscopic screen usually shows us that theintestine is more or less like a rigid tube.The walls are thickened and have lost theirnormal flexibility. One infers that the serrated appearanceis due to inflanmiatory thickening and in-duration in and about the intestinal wall,secondary to the presence of diverticula. Thediverticula themselves not being visible, per

. Text-book of normal histology: including an account of the development of the tissues and of the organs. Section of jaw of rabbit embryo,showing thickening of ectodermicepithelium {ec) from which dentalridge (e) begins its growth intomesoderm (;«). I50 NORMAL HISTOLOGY. the ridge. These secondary aggregations are the first indicationsof the enamel organs of the temporary teeth. After the estabUsh- FlG. iSo. Fig. i8i.. Model of jaw of human embrjo of 40 mm.: r, r, arch ofincreased epiihelium constituting dental ridge; /. local thick-enings corresponding to positions of future enamel sacs.(Aft Stock Photo

RM2CEGJEB–. Text-book of normal histology: including an account of the development of the tissues and of the organs. Section of jaw of rabbit embryo,showing thickening of ectodermicepithelium {ec) from which dentalridge (e) begins its growth intomesoderm (;«). I50 NORMAL HISTOLOGY. the ridge. These secondary aggregations are the first indicationsof the enamel organs of the temporary teeth. After the estabUsh- FlG. iSo. Fig. i8i.. Model of jaw of human embrjo of 40 mm.: r, r, arch ofincreased epiihelium constituting dental ridge; /. local thick-enings corresponding to positions of future enamel sacs.(Aft

. Identification of the economic woods of the United States, including a discussion of the structural and physical properties of wood . ery largely of lignin, the secondary wall.This thickening may proceed uniformly, or, asis usually the case, small gaps, called pits,occur. A pit is merely an unthickenedportion of the cell wall. Pits are of twoprincipal types, simple and bordered (Fig. 11). Fig. 9.—Tangen-tial section of a fusi-form ray from Pinusponderosa (westernyellow pine); r. d.,horizontal resin duct; e., epithelialcells; i. t., ray tra-cheids; the remain-der of the cells areray-parenchym Stock Photo

RM2CDCY2T–. Identification of the economic woods of the United States, including a discussion of the structural and physical properties of wood . ery largely of lignin, the secondary wall.This thickening may proceed uniformly, or, asis usually the case, small gaps, called pits,occur. A pit is merely an unthickenedportion of the cell wall. Pits are of twoprincipal types, simple and bordered (Fig. 11). Fig. 9.—Tangen-tial section of a fusi-form ray from Pinusponderosa (westernyellow pine); r. d.,horizontal resin duct; e., epithelialcells; i. t., ray tra-cheids; the remain-der of the cells areray-parenchym

$. The American journal of roentgenology, radium therapy and nuclear medicine . Fig. 7. Thickening in semilunar. Fig. 8. Os trigonum. Fig. 9. Secondary os calcis. ately rare in the adult (Fig.2). It is a per-fectly formed little bone like a sesamoid.It must not be confused with a fracturedstyloid. In the latter the rough edge of thefracture is evident. In old cases of fracturethe rough edge disappears, but the styloidremains deformed. Examination of both wrists should bemade when the presence of an extra bone issuspected, and if it is present on one side itwill usually be found on the other sid Stock Photo$

RM2CRNM4F–. The American journal of roentgenology, radium therapy and nuclear medicine . Fig. 7. Thickening in semilunar. Fig. 8. Os trigonum. Fig. 9. Secondary os calcis. ately rare in the adult (Fig.2). It is a per-fectly formed little bone like a sesamoid.It must not be confused with a fracturedstyloid. In the latter the rough edge of thefracture is evident. In old cases of fracturethe rough edge disappears, but the styloidremains deformed. Examination of both wrists should bemade when the presence of an extra bone issuspected, and if it is present on one side itwill usually be found on the other sid

. Journal of morphology . <i„ ,•«••-• • •,•••%?« ?? ttYi unyntt Ut;,tut tin itiu: tinJill. a The Jouknal of Moephology.—Vol. XX. No. 3. Fig. 10.. Fig. 8. HISTORY OF THE PROCEPHALIC LOBES OF EPEIRA CINEREA. A Study in xkachnid Embryology. AVERY E. LAMBERT. TABLE OF CONTENTS. PAGE I. Historical Statement 413 II. Materials and Methods 419 III. Origin of the Germ Layers, and Formation of the Cephalic Plate 422 Part 1. Formation of the Blastoderm 422 Part 2. Formation of tlie Blastodisc 423 Part 3. Formation of the Primary Thickening, or Primitive Cumulus 425 Part 4. Formation of the Secondary, Stock Photo

RM2CDG268–. Journal of morphology . <i„ ,•«••-• • •,•••%?« ?? ttYi unyntt Ut;,tut tin itiu: tinJill. a The Jouknal of Moephology.—Vol. XX. No. 3. Fig. 10.. Fig. 8. HISTORY OF THE PROCEPHALIC LOBES OF EPEIRA CINEREA. A Study in xkachnid Embryology. AVERY E. LAMBERT. TABLE OF CONTENTS. PAGE I. Historical Statement 413 II. Materials and Methods 419 III. Origin of the Germ Layers, and Formation of the Cephalic Plate 422 Part 1. Formation of the Blastoderm 422 Part 2. Formation of tlie Blastodisc 423 Part 3. Formation of the Primary Thickening, or Primitive Cumulus 425 Part 4. Formation of the Secondary,

. Comparative anatomy of the vegetative organs of the phanerogams and ferns. Plant anatomy; Phanerogams; Ferns. ANOMALOUS THICKENING IN DICOTFLEDONS AND GFMNOSPERMS. 603 the radial bands of parenchyma of the highly parenchymatous wood, which extend from the pith, the consequent splitting and disrupture first of the medullary sheath, then of the outer regions of wood, the appearance of new cambial zones close to the separated segments of wood, which form also new bast, and finally also the appearance of new strands of wood and bast in the pith itself, which are derived from secondary meristem, Stock Photo

RMREFE8R–. Comparative anatomy of the vegetative organs of the phanerogams and ferns. Plant anatomy; Phanerogams; Ferns. ANOMALOUS THICKENING IN DICOTFLEDONS AND GFMNOSPERMS. 603 the radial bands of parenchyma of the highly parenchymatous wood, which extend from the pith, the consequent splitting and disrupture first of the medullary sheath, then of the outer regions of wood, the appearance of new cambial zones close to the separated segments of wood, which form also new bast, and finally also the appearance of new strands of wood and bast in the pith itself, which are derived from secondary meristem,

. Comparative anatomy of the vegetative organs of the phanerogams and ferns;. Plant anatomy; Ferns. ANOMALOUS THICKENING IN DICOTYLEDONS AND GVMNOSPERMS. 603 the radial bands of parenchyma of the highly parenchymatous wood, which extend from the pith, the consequent splitting and disrupture first of the medullary sheath, then of the outer regions of wood, the appearance of new cambial zones close to the separated segments of wood, which form also new bast, and finally also the appearance of new strands of wood and bast in the pith itself, which are derived from secondary meristem, and have an Stock Photo

RMRE2N4W–. Comparative anatomy of the vegetative organs of the phanerogams and ferns;. Plant anatomy; Ferns. ANOMALOUS THICKENING IN DICOTYLEDONS AND GVMNOSPERMS. 603 the radial bands of parenchyma of the highly parenchymatous wood, which extend from the pith, the consequent splitting and disrupture first of the medullary sheath, then of the outer regions of wood, the appearance of new cambial zones close to the separated segments of wood, which form also new bast, and finally also the appearance of new strands of wood and bast in the pith itself, which are derived from secondary meristem, and have an

. Introduction to structural and systematic botany, and vegetable physiology. Botany. THICKENING OF THE WALLS OF CELLS. 35. lining. Every degree of this secondary deposition occurs, from a slight increase in the thickness of the membrane to the filhng up of the greater part of the cavity of the cell. Any hard wood furnishes illustrations of this. Indeed, the difference between sap- wood and heart-wood in trees is principally owing to the increase of this deposit, which converts the former into the latter; as may be seen by comparing, under the microscope, the tissue of the older with that of t Stock Photo

RMRDWN4C–. Introduction to structural and systematic botany, and vegetable physiology. Botany. THICKENING OF THE WALLS OF CELLS. 35. lining. Every degree of this secondary deposition occurs, from a slight increase in the thickness of the membrane to the filhng up of the greater part of the cavity of the cell. Any hard wood furnishes illustrations of this. Indeed, the difference between sap- wood and heart-wood in trees is principally owing to the increase of this deposit, which converts the former into the latter; as may be seen by comparing, under the microscope, the tissue of the older with that of t

. A Manual of botany : being an introduction to the study of the structure, physiology, and classification of plants . Botany. Fig. 7*. posits, and sometimes the layers are so produced as to leave uncovered spots, which communicate with the interior of the ceU by canals passing through the thickening layers, as in Cycas. In Eochea falcata (fig.. Fig. 76. <• 76) the epidermis, e e, consists of two layers of cells—the outer ones large, the imier small. The epidermis of Agave and Hoya is thickened by numerous secondary deposits; such is also the case with that of the branches of the mistleto. Stock Photo

RMRDJDRJ–. A Manual of botany : being an introduction to the study of the structure, physiology, and classification of plants . Botany. Fig. 7*. posits, and sometimes the layers are so produced as to leave uncovered spots, which communicate with the interior of the ceU by canals passing through the thickening layers, as in Cycas. In Eochea falcata (fig.. Fig. 76. <• 76) the epidermis, e e, consists of two layers of cells—the outer ones large, the imier small. The epidermis of Agave and Hoya is thickened by numerous secondary deposits; such is also the case with that of the branches of the mistleto.

. Text-book of botany, morphological and physiological. Botany. SECONDARY INCREASE IN THICKNESS OF STEMS AND ROOTS. 139 into permanent tissue, and indeed into thick-walled parenchyma, which now forms the secondary fundamental tissue between the secondary fibro-vascular bundles. Since the cells of the thickening-ring which face inwards pass over in centrifugal succession into permanent tissue, while the outermost divide repeatedly, the whole, ring continually moves centrifugally as it increases in diameter, and leaves behind new bundles and parenchymatous cells. In Yucca Millardet found the ori Stock Photo

RMRPXRK1–. Text-book of botany, morphological and physiological. Botany. SECONDARY INCREASE IN THICKNESS OF STEMS AND ROOTS. 139 into permanent tissue, and indeed into thick-walled parenchyma, which now forms the secondary fundamental tissue between the secondary fibro-vascular bundles. Since the cells of the thickening-ring which face inwards pass over in centrifugal succession into permanent tissue, while the outermost divide repeatedly, the whole, ring continually moves centrifugally as it increases in diameter, and leaves behind new bundles and parenchymatous cells. In Yucca Millardet found the ori

RMRDGA96–. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative. EYE 209 centripetally towards the brain; centrifugal fibres also arise later. In the course of further development, the epiblastic thickening mentioned above, which is often at first hollow, becomes separated from the epiblast, sinks more and more into the interior of the optic vesicle, and is diflferentiated to form the crystalline lens (Fig 167, b). The remaining space within the optic vesicle becomes filled by mesoblastic tissue, which grows in from the ventral side of the secondary optic vesicle through the so-call

RMRDFXYK–. The pathology and differential diagnosis of infectious diseases of animals : prepared for students and practitioners of veterinary medicine . Veterinary medicine; Communicable diseases in animals. 122 GLANDERS lymph glands becomes infiltrated •with small cells and subsequently thickened. In rare cases secondary chronic farcy occurs. It is marked by a large, diffuse new growth of connective tissue with nodular thickening of the skin. This condition is termed glander- ous elephantiasis or pachyderma. It chiefly affects the limbs and head. Of the abdominal organs, the spleen is most frequently

. The Cambridge natural history. Zoology. 392 FISHES condition of the Cyclostomes is probably a secondary acquisition. At the earliest embryonic stage at which any trace of an olfactory organ is apparent, there is a median thickening of the epidermis, possibly a vestige of some older sensory organ comparable, it may be, to the so-called olfactory organ of Amphioxus ; on each side of it there is a lateral thickening, the rudiments of the paired organs.i The three thickenings, or " plakodes," then sink inwards to form an olfactory pit. The partial subdivision of the adult organ by a ve Stock Photo

RMRDMB4D–. The Cambridge natural history. Zoology. 392 FISHES condition of the Cyclostomes is probably a secondary acquisition. At the earliest embryonic stage at which any trace of an olfactory organ is apparent, there is a median thickening of the epidermis, possibly a vestige of some older sensory organ comparable, it may be, to the so-called olfactory organ of Amphioxus ; on each side of it there is a lateral thickening, the rudiments of the paired organs.i The three thickenings, or " plakodes," then sink inwards to form an olfactory pit. The partial subdivision of the adult organ by a ve

. Botany of the living plant. Botany; Plants. 596 BOTANY OF THE LIVING PLANT point of a twig lies buried as a minute speck within the bud itself, which is less than three millimetres in diameter. But the Beech has the advantage of cambial thickening, which Ferns and Palms have not. Hence the pro- blem of provision of channels of supply to stem and leaves differs in the two types : the one shows " exogenous " growth, after the old terminology : the other is " endogenous ". While the former depends upon secondary cambial increase and accretion of successive layers of conducti Stock Photo

RMRH7YKA–. Botany of the living plant. Botany; Plants. 596 BOTANY OF THE LIVING PLANT point of a twig lies buried as a minute speck within the bud itself, which is less than three millimetres in diameter. But the Beech has the advantage of cambial thickening, which Ferns and Palms have not. Hence the pro- blem of provision of channels of supply to stem and leaves differs in the two types : the one shows " exogenous " growth, after the old terminology : the other is " endogenous ". While the former depends upon secondary cambial increase and accretion of successive layers of conducti

. Elementary botany : theoretical and practical. A text-book designed primarily for students of science classes connected with the science and art department of the committee of council on education . Botany. Secondary Deposit 19 (fig. 28). Or else it is deposited as separate rings, when an annular cell is formed (fig. 29). When the thickening is arranged in an irregular manner, producing a perfect network over the wall, the cell is said to be reticulated.. Fig. 2^.—Transverse section of a cell of the pith of Clevtatis vitalba : p, primary cell wall; /, innermost thickening layer ; p, pore-can Stock Photo

RMRDJ4T8–. Elementary botany : theoretical and practical. A text-book designed primarily for students of science classes connected with the science and art department of the committee of council on education . Botany. Secondary Deposit 19 (fig. 28). Or else it is deposited as separate rings, when an annular cell is formed (fig. 29). When the thickening is arranged in an irregular manner, producing a perfect network over the wall, the cell is said to be reticulated.. Fig. 2^.—Transverse section of a cell of the pith of Clevtatis vitalba : p, primary cell wall; /, innermost thickening layer ; p, pore-can

. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. COMPARATIVE ANATOMY 335 out by two distinct zones of cambial activity, the one immediately sur- rounding the primary xylem, and resulting in a band of radially seriated secondary wood, contiguous usually with the protoxylem of the primary development. Externally an exiguous secondary phloem appears (Fig. 176). Outside the thickening ring of the stele a second zone of cambial activity arises in the cortex, below the persistent bases of the leaves : this results in the formation of a broad band of secon Stock Photo

RMRDXG5K–. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. COMPARATIVE ANATOMY 335 out by two distinct zones of cambial activity, the one immediately sur- rounding the primary xylem, and resulting in a band of radially seriated secondary wood, contiguous usually with the protoxylem of the primary development. Externally an exiguous secondary phloem appears (Fig. 176). Outside the thickening ring of the stele a second zone of cambial activity arises in the cortex, below the persistent bases of the leaves : this results in the formation of a broad band of secon

. Comparative anatomy of the vegetative organs of the phanerogams and ferns. Plant anatomy; Phanerogams; Ferns. ANOMALOUS THICKENING IN DICOTVLEDONS AND GYMNOSPERMS.. thicker. But later a change takes place: a dry piece of a stem or branch of S. nux vomica of 135™"^ diameter, which was investigated, had a bast zone about 5™"^ thick, consisting of very many layers. Climbing species, such as S. toxifera, S. brachiata, &c., seem to form secondary bast in still larger quantities. The secondary layer of bast has, except in one essential point, the same structure, and shows the same ph Stock Photo

RMREFEA1–. Comparative anatomy of the vegetative organs of the phanerogams and ferns. Plant anatomy; Phanerogams; Ferns. ANOMALOUS THICKENING IN DICOTVLEDONS AND GYMNOSPERMS.. thicker. But later a change takes place: a dry piece of a stem or branch of S. nux vomica of 135™"^ diameter, which was investigated, had a bast zone about 5™"^ thick, consisting of very many layers. Climbing species, such as S. toxifera, S. brachiata, &c., seem to form secondary bast in still larger quantities. The secondary layer of bast has, except in one essential point, the same structure, and shows the same ph

. Comparative anatomy of the vegetative organs of the phanerogams and ferns;. Plant anatomy; Ferns. SECONDARV THICKENING. NORMAL DICOTYLEDONS. 4<53 to this, even casual observation shows that the secondary growth on the side of the â wood is almost always far more abundant than on the side of the bast. Both the successively developed elements of the wood and bast, and the cells of the initial layer, in certain cases, increase for a time in size, while growth in thickness proceeds, as will be described in greater detail below; from a definite period onwards, however, a constant average size Stock Photo

RMRE2NAH–. Comparative anatomy of the vegetative organs of the phanerogams and ferns;. Plant anatomy; Ferns. SECONDARV THICKENING. NORMAL DICOTYLEDONS. 4<53 to this, even casual observation shows that the secondary growth on the side of the â wood is almost always far more abundant than on the side of the bast. Both the successively developed elements of the wood and bast, and the cells of the initial layer, in certain cases, increase for a time in size, while growth in thickness proceeds, as will be described in greater detail below; from a definite period onwards, however, a constant average size

. A textbook of botany for colleges and universities ... Botany. 346 PHYSIOLOGY accompanied by an increase of the conducting tissues (sec Part I, p. 243). Annual thickening. — In trees and shrubs the xylem undergoes sec- ondary thickening in the first season of growth, and this is resumed in the second season, and so on, from the persistent cambium. Thus arises a great cylinder of xylem, which constitutes .the wood of the trunk and. Fig. 644. — Cross section of stem of Ricinus communis, showing ring of secondary xylem; for description, see fig. 541. — From Part I. branches. In many trees the x Stock Photo

RMRDXT3E–. A textbook of botany for colleges and universities ... Botany. 346 PHYSIOLOGY accompanied by an increase of the conducting tissues (sec Part I, p. 243). Annual thickening. — In trees and shrubs the xylem undergoes sec- ondary thickening in the first season of growth, and this is resumed in the second season, and so on, from the persistent cambium. Thus arises a great cylinder of xylem, which constitutes .the wood of the trunk and. Fig. 644. — Cross section of stem of Ricinus communis, showing ring of secondary xylem; for description, see fig. 541. — From Part I. branches. In many trees the x

. Identification of the economic woods of the United States : including a discussion of the structural and physical properties of wood . Wood; Trees. 32 ECONOMIC WOODS OF THE UNITED STATES Intermediate forms exist whose reference to either group is arbitrary. A simple pit is one in which the thickening about a spot on the primary wall forms a canal which is equally wide throughout its length, or narrowing outward (Fig. 11, H). The length of the canal is determined by the thickness of the secondary wall. When simple pits occur in very thick-walled cells, there is often a tend- ency to a slight Stock Photo

RMRDNMAH–. Identification of the economic woods of the United States : including a discussion of the structural and physical properties of wood . Wood; Trees. 32 ECONOMIC WOODS OF THE UNITED STATES Intermediate forms exist whose reference to either group is arbitrary. A simple pit is one in which the thickening about a spot on the primary wall forms a canal which is equally wide throughout its length, or narrowing outward (Fig. 11, H). The length of the canal is determined by the thickness of the secondary wall. When simple pits occur in very thick-walled cells, there is often a tend- ency to a slight

Secondary thickening Stock Photos and Images

Secondary thickening Stock Photos and Images

Download Confirmation

Password Confirmation

Search Results for Secondary thickening Stock Photos and Images (107)

Filter by agency collections

Search builder

Get great features with your free account

Get inspired for your next project!