File:Lectures on the physiology of plants (1887) (14594535380).jpg

Identifier: lecturesonphysio00sach (find matches)
Title: Lectures on the physiology of plants
Year: 1887 (1880s)
Authors: Sachs, Julius, 1832-1897
Subjects: Plant physiology
Publisher: Oxford : The Clarendon Press
Contributing Library: NCSU Libraries
Digitizing Sponsor: NCSU Libraries

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/. Particular stress was formerly laid on the fact that both in Pandorina and inthe Conjugatae (e.g. Spirogyra), the two cells which unite sexually are equal in size 73° LECTURE XLI. and are apparently also similarly constituted, and such sexual acts were namedConjugation, in contrast to the ordinary acts of Fertilisation which exclusively occurin Mosses and Vascular Cryptogams particularly, where the one of the two sexualcells, relatively large and non-motile, functions as the Oosphere, and is fertilised bya relatively very minute and actively moving zoosperm (antherozoid). The investi-gations of late years, however, have brought to light numerous cases from whichit must be concluded that no essential difference exists between conjugation andordinary fertilisation by means of antherozoids; this may be concluded from thefact, among others, that both forms of sexual process occur in very closely alliedspecies. Goebel found, for instance, in the case of one of the Volvocineoe which is
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female colony (ca-nobiuni) a(after Goebt;!). closely allied to the Pcmdorina described above, and, like that, consists of a revolvingcoenobium, that the sexual cells are differentiated into oospheres and relatively minuteantherozoids. The plant in question, Eiidorina elegafis, consists of gelatinous vesiclesof elUpdcal shape, in which are contained i6 or 32 cells, each of which possesses twocilia, which project through holes in the envelope far into the surrounding water.Active multiplicadon occurs by the asexual method, each individual cell of a familybecoming transformed by appropriate divisions into a family consisting of 16 or32 cells again: these young families are set free by the disintegration of the parentenvelope. Sooner or later, however, a sexual difference makes its appearancebetween different coenobia : some become male, others female. In the latter, 16 or32 cells assume the character of oospheres, not conspicuously different from ordinary EUDORINA. 31 vegetative cells. I

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