The power of movement in plants / by Charles Darwin ; assisted by Francis Darwin.

  • Charles Darwin
Date:
1880
Catalogue details

Licence: Public Domain Mark

Credit: The power of movement in plants / by Charles Darwin ; assisted by Francis Darwin. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

    18/644 page 2
    axes directed to different points of the compass. Whilst describing such figures, the apex often travels in a zigzag line, or makes small subordinate loops or triangles. In the case of leaves the ellipses are generally narrow. Until recently the cause of all such bending move- ments was believed to be due to the increased growth of the side which becomes for a time convex; that this side does temporarily grow more quickly than the concave side has been well established; but De Vries has lately shown that such increased growth follows a previously increased state of turgescence on the convex side.* In the case of parts provided with a so-called joint, cushion or pulvinus, which consists of an aggregate of small cells that have ceased to increase in size from a very early age, we meet with similar movements; and here, as Pfeffer has shown f and as we shall see in the course of this Avork, the increased turgescence of the cells on opposite sides is not followed by increased growth. Wiesner denies in certain cases the accuracy of De Vries' con- clusion about turgescence, and maintains t that the increased extensibility of the cell-walls is the more important element. That such extensibility must accompany increased tm'gescence in order that the part may bend is manifest, and this has been insisted on by several botanists ; but in the case of unicellular j)lants it can hardly fail to be the more important element. On the whole we may at present conclude that in- * Sachs first showed (' Lehr- 19, 1879, p. 830. l)uch,' &c., 4th edit. p. 452) the t ' Die Periodisclien Beweguu- intiniate connection between tur- gen der Blattorgane,' 1875. gescence and growth. For De I ' Untersuchungen iiber den Vlies' interesting essay, ' Waohs- Heliotropismus,' Sitzb. der K. tliumskriimmungen melirzelliger Akad. der Wisseuschaft. (Vienna), Urgane,' see ' Bot. Zeitung,' Dec. Jan. 1880.
    digitised image 1
    digitised image 2
    digitised image 3