. Les plantes et leurs usages ; une introduction à la botanique. La botanique, la botanique, économique. 1,99 UI. 340 III.--Umbrellii-hépatique. Anthcridium (-"VO- numer irte montrant "nathin cellules qui produisent des sperniatozoids. (Atkinson). Fig. 340, IV.-hépatique de parapluie. Spermatozoïdes, highb' agrandie. (Atkinson.) d'extension (Fifj. .341, I-V), mais thej- viennent enfin de se coucher dessous à travers le bas du pliage des bords des lobes. Les gamétanges femelles sont ainsi protégés par leur position, et à côté de.s ce qu'ils sont couverts par un rideau suspendu (Fig. .341, V, p). Lorsque les plantes sont mouillées avec pluie ou

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. Plants and their uses; an introduction to botany. Botany; Botany, Economic. ¥ui. 340, III.—-Umbrellii-liverwort. Anthcridium (-"VO showing tlir numer- ous cells "nathin which produce sperniatozoids. (Atkinson.) Fig. 340, IV.—Umbrella-liverwort. Spermatozoids, highb' magnified. (Atkinson.) expansion (Fifj. .341, I-V), but thej- come finally to lie underneath through the folding downward of the edges of the lobes. The female gametangia are thus protected by their position, and beside.s this they are covered by a hanging curtain (Fig. .341, V, p). When the plants are wet with rain or dew the flagellate male gametes are set free and swim or crawl from their elevated home down the stalk and to a female plant; then they climb up its stalk (doubtless aided by numerous hairs thereon) to the archegonia. The fer- tilized egg-cell gives rise to a spheroidal embr3'o which develops into a sporoph3'te resembling that of Ricoia for a while but finally, by growth of the basal region of the capsule, producing a foot- stalk whose elongation pushes the sporangium through the top of the calyptra (Fig. 341, III). Meanwhile, elongated cells, called elafers i (Fig. 341, IV), having elastic, spirally thickened walls are being formed among the spores; and when finally the cap- sule bursts open these elaters, by mechanical movements due to drying, eject the spores and so help to scatter them. The sporo- phyte is fed entirely by the gametophyte and lives as a parasite, the foot or lower end of the stalk serving as an haustorium. Especial interest attaches to the genus Anthoceros (often called horned liverworts from the form of the sporophyte), because these humble plants have preserved structures which help us to under- stand how all the higher plants may have originated. The game- ^ E-la'ter < Gr. elater, a driver.. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of thes

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• bookcentury1900
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