. A textbook of botany for colleges and universities ... Botany. 36 MORPHOLOGY after the partition wall is formed, it becomes uninucleate by the degeneration of the other nuclei. In the wall of the oogonium a more or less beaked opening is formed by which the sperms enter. The antheridial branch is similar in origin, but is longer, the antlieridium being cut off at the curved tip by a wall as a small cell. In other species a single branch bears both oogonia and antheridia (fig. 98), a common arrangement of the cluster being a terminal antheridium and a group of laterally developed oogo
. A textbook of botany for colleges and universities ... Botany. 36 MORPHOLOGY after the partition wall is formed, it becomes uninucleate by the degeneration of the other nuclei. In the wall of the oogonium a more or less beaked opening is formed by which the sperms enter. The antheridial branch is similar in origin, but is longer, the antlieridium being cut off at the curved tip by a wall as a small cell. In other species a single branch bears both oogonia and antheridia (fig. 98), a common arrangement of the cluster being a terminal antheridium and a group of laterally developed oogonia. In each. Figs. 98-100. — Vaucheria: 98, 99, two methods of forming oogonia and antheridia; in both cases the terminal antheridium has discharged its sperms (100). — 100, after WORONIN. antheridium numerous sperms are formed (fig. 100), which are dis- charged, enter through the beaked openings of the oogonia, and fertilize the eggs. The heavy-walled oospore is the protected stage of the plant and germinates directly into a new filament. Experiments. —The experiments upon Vaucheria are of great interest, since by varying the character of the medium, the nature of the nutrition, the light, etc., there may be produced at will sterile plants, zoospore-producing plants, or gamete- producing plants. Vaucheria also has great power of resisting unfavorable condi- tions, in the presence of which the filament becomes chambered by the formation of thick cross walls, and the contents of each compartment round up as an aplano- spore. In favorable conditions each aplanospore either forms a new filament directly, or discharges an amoeba-like protoplast, which rounds off as a green sphere, covers itself with a wall, and either forms a filament directly or enters again into a period of rest. This ability to respond promptly to varying conditions and to change the program at almost any period in the life history is very marked among the lower Please note that these images are
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