The Mode of Occurrence of Tannin in the Living Cell

The Mode of Occurrence of Tannin in the Living Cell

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1922 edition. Excerpt: ...of temperature, etc., even after many hours of watching. That slow amoeboid movements may occur in response to certain natural stimuli is quite possible. Indeed, it is well known that the flat chloroplastic band of Mougeatia slowly orients itself with regard to light, while those of higher plants also change position and are said to be amoeboid. That in the case of Spirogyra the chloroplasts are not normally fluid is proved by other than the above merely negative observation. When the cells are plasmolysed it is common to find some whose chloroplasts are too rigid to contract with the cytoplasm but maintain their position more or less, while the cytoplasm is pulled in between the coils. The spiral form itself I take to be an expression of elasticity, being the position of minimum curvature, and so of least resistance, for an elastic body confined in a closed cylinder shorter than itself. Thus in species whose chloroplasts are no longer than the cell they are straight and longitudinal, the more their length exceeds that of the cell the closer the spiral. From all these considerations it would seem that under ordinary conditions the physical state of the chloroplasts is that of an elastic gel.' The changes in form.--The "contraction" which is observed in abnormal chloroplasts is not a simple phenomenon but is of two very different types. In type I the body behaves as a liquid and the contraction is manifestly an endeavour to assume minimal area. The sinuosities of margin first smooth out, the whole chloroplast thickens and shortens, becomes cylindrical and finally spherical, or else constricts into several spheres. During the longitudinal contraction the coils may slip round the plasmatic layer if the spiral is loose; if it...
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Product details

  • Paperback | 90 pages
  • 189 x 246 x 5mm | 177g
  • United States
  • English
  • black & white illustrations
  • 1236792351
  • 9781236792358