Nature and development of plants . gh an opening that forms at the apex of the branch. 176 SEXUAL REPRODUCTION A gametangium that produces clearly differentiated male gametesis called an antheridium (pin. antheridia) and the gametes arefrequently called antherozoids or sperms. A single femalegamete is found in a similar branch which becomes rather egg-shaped and at maturity opens at the beaked end (Fig. 114, B).A single-celled female gametangium is called an oogonium andthe female gamete is frequently referred to as the oosphere oregg. The male gametes are discharged a few minutes after theoog
Nature and development of plants . gh an opening that forms at the apex of the branch. 176 SEXUAL REPRODUCTION A gametangium that produces clearly differentiated male gametesis called an antheridium (pin. antheridia) and the gametes arefrequently called antherozoids or sperms. A single femalegamete is found in a similar branch which becomes rather egg-shaped and at maturity opens at the beaked end (Fig. 114, B).A single-celled female gametangium is called an oogonium andthe female gamete is frequently referred to as the oosphere oregg. The male gametes are discharged a few minutes after theoogonium opens, when they swarm about the open end of thefemale gametangium and readily enter it. As soon as fusion hasbeen effected the gametospore becomes invested with a thick walland in this condition can endure a limited drought. In germi-nating it develops directly into a new plant. This feature of thelife history of Vauchcria is therefore of a more primitive naturethan in the case of Ulothrix. In the following studies vou will. Fig. 114. Sexual reproduction of Vaucheria: A, portion of a filamentthat has formed two branches which have grown into a male, an, andfemale, og, gametangia. B, later stage, the gametangia have opened, per-mitting the escape of the male gametes and the fertilization of femalegamete. C, gametospore detached from the filament. repeatedly notice variations of this nature. In the developmentof plants advances are often confined to one or another featureof their organism which may become highly developed and spe-cialized; at the same time one or more features may be retainedthat have been subject to little or no variation and which, there-fore, remain in a primitive state. DEVELOPMENT OF PLANTS 177 71. Other Members of the Green Algae.—There are severalorders of the Chlorophyceae, some of which are marine, thatcannot be considered at this time. Two genera, however,deserve attention because they show significant advances inthe evolution of plant life. In
Size: 1968px × 1270px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookpublisher, booksubjectplants
