. A practical course in botany, with especial reference to its bearings on agriculture, economics, and sanitation. Botany. THE ROOT 63 the office of the stem, until there is practically no difference between them. On the sides of guUies, where the earth has been washed from around the trees, we often see the upper portion of the root covered with a thick bark and ful- filling every office of a true stem. 67. Minute structure of the root. — (a) Mount in water and place under the microscope a portion of the root of an oat or radish seedling containing a number of hairs. In studying the thin, tra

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. A practical course in botany, with especial reference to its bearings on agriculture, economics, and sanitation. Botany. THE ROOT 63 the office of the stem, until there is practically no difference between them. On the sides of guUies, where the earth has been washed from around the trees, we often see the upper portion of the root covered with a thick bark and ful- filling every office of a true stem. 67. Minute structure of the root. — (a) Mount in water and place under the microscope a portion of the root of an oat or radish seedling containing a number of hairs. In studying the thin, transparent roots of very young seedlings a section will not be necessary. Observe whether the hairs originate from the epidermis or from the interior. Are they true roots, or mere outgrowths from the cells of the epidermis? Do they consist of a single cell or a number of cells each? Notice what very thin cell walls the hairs have; is there any advan- tage in this ? The interior, trans- parent portion of the hair con- tains the sap, and the protoplasm forms a thin lining on the inner ^ „ -n T - .. ,. , 0 Fig. 79. — Longitudinal section SUriaCe OI the Wall; Why not through the tip of a young root, some- tr>P wn tipyt trip wall nnrl tliA what diagrammatic : h, h, root hairs ; tne Sap next tne Wail ana tne ePi epidermis; a, cortex; b, central protoplasm in the interior ? (58, cy1™der; «, sheath of the cylinder fin -. (endodermis); g, growing point; c, OU.J root cap; d, dead and dying cells loos- (6) Next examine a portion <^d from the extremity of the cap. of the body of the root and try to make out the parts as shown in Fig. 79, and compare them with your observa- tions in 64. The light line running through the middle is the central cylinder, up which the water passes, as was shown by the colored liquid in 64. Outside this is a darker por- tion (a, Fig. 79), corresponding to the cortex (rr, Fig. 77). Besides other uses, the cortex serves to prevent the loss of water a

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