. Lectures on the evolution of plants. Botany; Plants. 54 EVOLUTION OP PLANTS 9, C, an), and closely resemble the zoospores except in size, and the partial or complete loss of chlorophyll. The spermatozoid has a large nucleus with relatively little cytoplasm, as the nucleus is probably of the most impor- tance in the act of fecundation. At maturity the oogonium opens and permits the en- trance of the motile spermatozoid, which at once pene- trates into the egg-cell where its nucleus fuses with that of the egg, thus fertilizing it. As the result of fertilization the egg becomes in- vested with
. Lectures on the evolution of plants. Botany; Plants. 54 EVOLUTION OP PLANTS 9, C, an), and closely resemble the zoospores except in size, and the partial or complete loss of chlorophyll. The spermatozoid has a large nucleus with relatively little cytoplasm, as the nucleus is probably of the most impor- tance in the act of fecundation. At maturity the oogonium opens and permits the en- trance of the motile spermatozoid, which at once pene- trates into the egg-cell where its nucleus fuses with that of the egg, thus fertilizing it. As the result of fertilization the egg becomes in- vested with a heavy cell-wall and forms a resting- spore which re- mains dormant for a long period, and is capable of re- sisting, unharmed, f reezingand drying up. In the highest type of all, repre- sented by the pecu- liar genus Coleo- chsete (Fig. 10), the oogonium, with the contained oospore, becomes, after fertilization, invested with a protective covering formed by the growth of adjacent cells, so that the influence of the act of fertilization ex- tends beyond the egg-cell. Coleochsete, as we shall see. Fig. 10. — A, a plant of Coleochsdte scutata, one of the highest of the Confervaoese; B, fragment of another species, C. pulvinata, with an oogonitim, og; C, the germinating spore seen in section, showing its division into a nearly globular cell-mass; each cell later gives rise to a single biciliate zoospore. (Figs. B and C after Oltmanns.). 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, London, The Macmillan company
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Keywords: ., bookcentury1900, bookdecade, booksubjectbotany, booksubjectplants
