. Lectures on the evolution of plants. Botany; Plants. 150 EVOLUTION OF PLANTS filled with accumulated food substances which serve to supply the developing female gametophyte with food, as the latter does not contain chlorophyll. The gam- etophyte, as in Selaginella, is almost entirely included within the large macrospore, and the formation of the. Fig. 39 (Heterosporous Ferns). — A, sporophyte of Isoetes echinospora; B, a single leaf showing the enlarged base bearing a single macrosporan- gium, ma; the mierosporangia are much the same; C, a germinated microspore with the contained gametophyte
. Lectures on the evolution of plants. Botany; Plants. 150 EVOLUTION OF PLANTS filled with accumulated food substances which serve to supply the developing female gametophyte with food, as the latter does not contain chlorophyll. The gam- etophyte, as in Selaginella, is almost entirely included within the large macrospore, and the formation of the. Fig. 39 (Heterosporous Ferns). — A, sporophyte of Isoetes echinospora; B, a single leaf showing the enlarged base bearing a single macrosporan- gium, ma; the mierosporangia are much the same; C, a germinated microspore with the contained gametophyte reduced to a single vegeta^ tive cell, v, and an antheridium with four coiled spermatozoids; D, Marsilia vestita, a heterosporous form allied to the leptosporangiate ferns; sp, the " sporocarp " or modified leaf-segment within which are borne the sporangia; E, section of the upper part of the macrospore and female gametopliyte, here reduced to a single archegonium, ar; the body of the macrospore, .sp, remains undivided; F, sperraatozoid of Marsilia; x, the remains of the central part of the sperm-cell. cells is preceded by a repeated division of the nuclei as in the formation of the gametophyte or " endosperm " of the flowering plants. Germination, however, does not begin until the spores have been set free. The arche-. 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: 1672px × 1495px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade, booksubjectbotany, booksubjectplants
