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Geotropism and Growth1

Nature volume 25, pages 616617 | Download Citation



IF the punctum vegetationis of a root is removed by a transverse section, the root loses more or less completely the power of curving geotropically downwards when placed in a horizontal position. This curious experiment was originally made by Ciesielski, and has been confirmed by the observations described in “The Power of Movement in Plants” (chap. xi.). The theory founded by Mr. Darwin in these observations is that the punctum veg. is the part of the root which is sensitive to gravitation, and that a stimulus is thence transmitted to the region of growth where the geotropic curvature takes place. But it is evident that the facts are capable of a different interpretation, it might be supposed that cutting off the tip of the root acts merely as a shock, and prevents the occurrence of geotropism, just as any other severe injury might do so. This view has recently been brought forward by Wiesner (“Das Bewegungsvermögen der Pflanzen,” 1881, p. 97), and is supported by him with a number of experiments on the growth of decapitated roots. The results of some of Wiesner's experiments are given below, the figures representing the amount of growth per cent, in twenty-four hours:—

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