File:Lectures on the physiology of plants (1887) (14594596818).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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y. The gelatinous envelopes of the young families deliquesce,and the individual cells are thus set free, and each swarms by itself independently(///). These free swarmers differ much in size; they are rounded and green at theposterior end, and pointed, hyaline, and provided with a red corpuscle at the anteriorend which also supports the two cilia. During the swarming of these bodies, some PANDORINA. 729 are observed to approach one another in pairs, as if seeking each other ; they come incontact at their apices, and fuse into a zygote which is at first biscuit-shaped iJV) andwhich gradually contracts into a sphere (V), in which the two red corpuscles and thefour cilia at the enlarged hyaline spot are at first still perceptible, though they alldisappear soon afterwards. A few minutes after the beginning of the conjugation thezygote is a spherical cell (VI), which then remains dormant within its cell-wall fora long time, its green colour passing over into a brick-red one. On placing the
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FIG. 411.—Development of Pandorina Moriim (after Pringsheim)- / a swarming family; // a similar family divided intosixteen daughter-families ; /// a sexual family, the individual cells of which are escaping from the gelatinous investment;IV, K conjugation of pairs of swarmers ; VI a zygote which has just been completed; /// a fully grown zygote ; VI tltransformation of the contents of a zygote into a large swann-cell; l.\ the same after being set free ; .Ia young familydeveloped from the latter. dried up, and meanwhile considerably grown, spheres into water, germination beginsafter about twenty-four hours. The external shell of the cell-wall breaks away, anda layer within it swells up, and now contains one or two, or even three large swarm-spores, which finally escape (VIII and IX), and after swarming for a short timesurround themselves with a gelatinous envelope, and, by means of successivedivisions, break up into sixteen primordial cells, which now again form a fomilyas in Fig. /.

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