. An introduction to the structure and reproduction of plants. Plant anatomy; Plants. PELVETIA 20^ swollen fertile ends are a particularly conspicuous feature (Fig. log). The structure of the thallus shows no important differences, but the branches of the frond are much narrower and channelled on their upper surface, features which aid in the retention of mois- ture ; moreover, the thallus is thus mainly illuminated by oblique light, so that the heating effect of the sun, and therefore transpira- tion, is presumably diminished during the hot hours of the day. The principal differences exhibite
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. An introduction to the structure and reproduction of plants. Plant anatomy; Plants. PELVETIA 20^ swollen fertile ends are a particularly conspicuous feature (Fig. log). The structure of the thallus shows no important differences, but the branches of the frond are much narrower and channelled on their upper surface, features which aid in the retention of mois- ture ; moreover, the thallus is thus mainly illuminated by oblique light, so that the heating effect of the sun, and therefore transpira- tion, is presumably diminished during the hot hours of the day. The principal differences exhibited by Pelvetia can therefore be related to the special conditions of its habitat.. Fig. 109.—Plant of Pelvetia eanaliculata, about natural size, showing the basal attaching disc and the prominent fertile conceptacles. On rocky shores the Brown Algae Pelvetia, Fticus, and Lami- naria often form three zones at successively lower levels, occurring in the order named. Other members of the group are free-floating, as, for example, Sargassitm hacciferum (Fig. no), huge stretches of which characterise the Sargasso Sea in the ^Mid-Atlantic. Many of the larger Brown Algse are edible, and indeed extensively cultivated in Japan, whilst in the West of Scotland Fucus and similar forms are abundantly used as manure. Most of the Red Algae {Rhodophycea) are much smaller plants preferring weakly illuminated habitats, so that they either grow at considerable depths below low-tide level or in shady rock-pools.. 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.. Fritsch, Felix Eugene, 1879-; Salisbury, E. J. (Edward James), Sir, b. 1886. London, G. Bell and sons ltd.