. The elements of botany for beginners and for schools. Botany. 160 CRYPTOGAMOUS OR FLOWERLESS PLANTS. [SECTION 17. closely resembles a small Liverwort. This is named a Pkothallus (Fig. 509): from some point of this a bud appears to originate, which produces the first fern-leaf, soon followed by a second and third, and so the stem and leaves of the plant are set up. 490. Investigation of this prothallus under the microscope resulted in the discovary of a wholly unsusppcted kind of fertilization, taking place at. this germinating stage of the plant. On the under side of the prothallus two kinds
. The elements of botany for beginners and for schools. Botany. 160 CRYPTOGAMOUS OR FLOWERLESS PLANTS. [SECTION 17. closely resembles a small Liverwort. This is named a Pkothallus (Fig. 509): from some point of this a bud appears to originate, which produces the first fern-leaf, soon followed by a second and third, and so the stem and leaves of the plant are set up. 490. Investigation of this prothallus under the microscope resulted in the discovary of a wholly unsusppcted kind of fertilization, taking place at. this germinating stage of the plant. On the under side of the prothallus two kinds of organs appear (Fig. 510). One may be likened to an open and depressed ovule, with a single cell at bottom answering to nucleus ; the other, to an anther; but instead of pollen, it discharges corkscrew- shaped microscopic filaments, which bear some cilia of extreme tenuity, by the rapid vibration of which the filaments move freely over a wet surface. These filaments travel over the surface of the prothallus, and even to other prothalli (for there are natural hybrid Ferns), reach and enter the ovule- FiG. 511. Lycopodiiim Carolinianum, of nearly natural size. 512. Inside view of one of the bracts and spore-case, magnified. Fig. 513. Open 4-valved spore-case of a Selaginella, and its four large spores (macrospores), magnified. 514. Macrospores of another Selaginella. 515. Same separated. Fig. 516. Plant of Isoetes. 517. Base of a leaf and contained sporocarp filled with microspores ciit across, magnified. 518. Same divided lengthwise, equally magnified ; some microspores sren at the left. 519. Section of a spore-case contidn- ing macrospores, equally magnified; at the right three macrospores more 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 Gray, Asa, 1810-1888. New York American Book Co
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