. Lectures on the evolution of plants. Botany; Plants. 1-26 EVOLUTION OF PLANTS sp- duces a slender filament or cell-row, much like the sim- pler green algae. This condition soon gives place to a delicate flat thallus, closely resembling some of the simpler liver- worts. At this stage growth is effected by a single apical cell (Fig. 32, B, a:) precisely as in such simple liv- erworts as An- eura. The degree of development of this thalloid gametophyte varies much in Fig. 32. âa, the germinating spore of the ostrich dltterent lems, fern (Onoclea struthiopteris), showing the rup- \yyx^ jj; mav re
. Lectures on the evolution of plants. Botany; Plants. 1-26 EVOLUTION OF PLANTS sp- duces a slender filament or cell-row, much like the sim- pler green algae. This condition soon gives place to a delicate flat thallus, closely resembling some of the simpler liver- worts. At this stage growth is effected by a single apical cell (Fig. 32, B, a:) precisely as in such simple liv- erworts as An- eura. The degree of development of this thalloid gametophyte varies much in Fig. 32. âa, the germinating spore of the ostrich dltterent lems, fern (Onoclea struthiopteris), showing the rup- \yyx^ jj; mav reach tured spore-coat, sp, and the first rhizoid, r; B, -^ a somewhat older plant (gametophyte) with a a length of sev- single apical cell, x; C, female gametophyte seen from below, showing the archegonia, ar; eral Centimetres, D, young sporophyte, sp, still attached to the i â ,- gametophyte, ff; the sporophyte has developed Drancning ex- leaves and roots, r, so that it is quite inde- fâ,7-Ql-rr pendent of the gametophyte. Densiveiy, ana living for sev- eral years, especially when the archegonia remain unfer- tilized (Fig. 31, A). The largest of these "prothallia" occur in certain tropical ferns, especially species of filmy-ferns (Hymenophyllacese) and Vittaria. In the latter genus they sometimes have numerous branches, radiating from a common centre and forming circular disks ten centimetres or more in diameter, and closely resemble a large liverwort. These large gametophytes. 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 Campbell, Douglas Houghton, 1859-1953. New York, The Macmillan Co. , London, Macmillan & Co. , Ltd.
Size: 1590px × 1571px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade, booksubjectbotany, booksubjectplants
