The elements of botany for beginners and for schools . Fig. 509. A young prothallus of a Maiden-hair, moderately enlarged, and anolder one with the first fern-leaf developed from near the notch. 510. Middle por-tion of the young one, much magnified, showing below, partly among the rootlets,the antheridia or fertilizing organs, and above, near the notch, three piatiUidia,to be fertilized. 160 CRYPTOGAMOUS OR FLOWERLESS PLANTS. [SECTION 17. closely resembles a small Liverwort. This is named a PEOTHAliUS (): from some point of this a bud appears to originate, which producesthe first fern-l
The elements of botany for beginners and for schools . Fig. 509. A young prothallus of a Maiden-hair, moderately enlarged, and anolder one with the first fern-leaf developed from near the notch. 510. Middle por-tion of the young one, much magnified, showing below, partly among the rootlets,the antheridia or fertilizing organs, and above, near the notch, three piatiUidia,to be fertilized. 160 CRYPTOGAMOUS OR FLOWERLESS PLANTS. [SECTION 17. closely resembles a small Liverwort. This is named a PEOTHAliUS (): from some point of this a bud appears to originate, which producesthe first fern-leaf, soon followed by a second and third, and so the stemand leaves of the plant are set up. 490. Investigation of this prothallus under the microscope resulted inthe discovery of a wholly unsuspected kind of fertilization, taking place at. this germinating stage of the plant. On the under side of the prothallustwo kinds of organs appear (fig. 510). One may be likened to an openand depressed ovule, with a single cell at bottom answering to nucleus;the other, to an anther; but instead of pollen, it discharges corkscrew-siiaped microscopic filaments, which bear some cilia of extreme tenuity, bytlie rapid vibration of which the filaments move freely over a wet filaments travel over the surface of the prothallus, and even to otherprothalli (for there are natural hybrid Ferns), reach and enter the ovule- FlG. 511. Lycopodmm Carolinianum, of nearly natural size. 512. Inside viewof 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. 515. Sameseparated. Fig. 516. Plant of Isoetes. 517. Base of a leaf and contained sporooarp filledwith microspores cut across, magnified. 518. Same
Size: 1709px × 1461px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1880, booksubjectbotany, bookyear1887
