File:Hardwicke's science-gossip - an illustrated medium of interchange and gossip for students and lovers of nature (1867) (14782699052).jpg

Identifier: hardwickesscienc03cook (find matches)
Title: Hardwicke's science-gossip : an illustrated medium of interchange and gossip for students and lovers of nature
Year: 1867 (1860s)
Authors: Cooke, M. C. (Mordecai Cubitt), b. 1825 Taylor, J. E. (John Ellor), 1837-1895
Subjects: Science Natural history
Publisher: London : Robert Hardwicke
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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represented, inorder to show the root-like termination, and themanner in which the spiral bands are graduallydeveloped. In the two lowest cells the chlorophyllappears in a shapeless mass, in the third, the spiralbands begin to be marked, and in the middle of thefilament they appear as at b. At the growingpoint, they are distinctly marked, but somewhatcompressed. In the ordinary cells of this species,the spiral bands, which are rather lax at the endsof the cell, in the middle run close up to oneanother, and give a peculiar character to thefilament. The cells of different species are not always ter-minated in the same manner. In some a cell sepa-rated from the rest exhibits a rounded outline, inothers it is at first slightly constricted, and thenrounded (fig. 10). In the former case, the junctionof two cells is flat, but in the latter the cell-wall isfolded back. This may be readily observed, whenthe plant is treated with iodine (fig. 10,/). March 1,1867.) IIARDWICKES SCIENCE.GOSSIP. GL
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Fig 51. Spirogyea. All the species of Spirogyra exhibit the process ofconjugation. Two neighbouring plants throw outfrom the sides of their cells little processes (figs. 7,8) ; when these meet together a union is effected,the intervening cell-walls are absorbed, or ruptured, and the contents of one cell pass into the other.Before, however, this takes place, the spiral coilsare relaxed, and their curves turned towards theprocess; then the contents lose their symmetricalform, and become altogether shapeless (figs. 7, 9). 62 HABDWICKES SCIENCE-GOSSIP. (March 1, 1S67. When the conjugation is complete, the combinedcontents of the two cells become an oval spore(figs. 8, 12), from which a new plant eventuallysprings. Eig. 7 represents a curious instance of a filament,which has conjugated with two others. In ordinary cases the conjugation takes place ashas been just described, but in some cases it takesplace in two contiguous cells of the same filament(fig. 9), and the contents of one cell pa

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