The elements of botany for The elements of botany for beginners and for schools elementsbotany00gray Year: 1887 160 CRYPTOGAMOUS OR FLOWERLESS PLANTS. [SECTION 17. closely resembles a small Liverwort. This is named a Prothallus (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 tliis prothallus under the microscope resulted in the discovery of a wholly unsuspected kind of fertilization, takin? place at this germinating stage of the
The elements of botany for The elements of botany for beginners and for schools elementsbotany00gray Year: 1887 160 CRYPTOGAMOUS OR FLOWERLESS PLANTS. [SECTION 17. closely resembles a small Liverwort. This is named a Prothallus (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 tliis prothallus under the microscope resulted in the discovery of a wholly unsuspected kind of fertilization, takin? 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, whicli bear some cilia of extreme tenuity, by the rapid vibration of which the filaments move freely over a wet surface. Tiiese 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. Lycopodium 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 (niacrospores^^ magnified. 514. Macrospores of another Selaginella. Same separated. Fig, 516. Plant of Isoetes. 517. Base of a leaf and contained s]iorocarp filled with microspores cut across, magnified. 518. Same divided lengthwise, equally magnified; some microspores seen at the left. 519. Section of a spore-case contain- ing macrospores, equally maguilied; at the right three macrospores more magnified.
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