File:Lectures on the physiology of plants (1887) (14758296596).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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theone hand and by means of seedson the other. In the former caseindividual cells — i. e. the spores— become separated off from themother-plant, and the new plant-life begins, so to speak, entirelyanew. Here in the case of theseed-plants the seeds also separatefrom the mother-plant, of course,to carry on a new plant - life,but the young plant is alreadythere, and, in most cases, alreadyconsists of the first rudimentaryorgans, a primary shoot and radicle,and these organs are composed ofinnumerable minute cells in whichthe tissue-systems are already dif-ferentiated. The young plant which lies in the seed is already formed while the seed itself is still part of the parentplant, and is so far nourishcil by this that subsequently, on the germination ofthe seed, litde more than a mere enlargement of the embryo is necessary. Seed-plants may therefore in this sense be compared with viviparous animals. Acomparison of the Cryi)togams or spore-plants with oviparous animals, however, (3) ^ 3C
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Fig. I through the tits Ptjtea, I median longitudinal sectionseed, >■ being the micropjle end. // commencement of germination, theroot emerging, /// conclusion of germination, after the endosperm hasbeen exhausted (the seed was not deep enough in the soil, and was there-fore carried up by the cotyledons as the stem elongated). A shows theruptured testa at s. B shows the endosperm e after the removal of one halfof the testa. C longitudinal section of endosperm and embryo ; and Dtransverse section of the same, at the beginning of germination ; c coty-ledons ; tu primary root; .vthe embryo-sac pushed aside by the root (it isruptured at ^.v) ; he hypocolyl; iv secondary roots; r red membranelining the hard testa. 754 LECTURE XLII. would be but a very lame one, since spores are not eggs at all; it is only inthe lowest regions of the vegetable kingdom, especially in the Fucacese and afew other forms, that oospheres are separated from the mother-plant. From these preliminaries we may no

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