Plant autographs and their revelations / by Sir Jagadis Chunder Bose.

  • Bose, Jagadis Chandra, 1858-1937.
Date:
1927
Catalogue details

Licence: In copyright

Credit: Plant autographs and their revelations / by Sir Jagadis Chunder Bose. Source: Wellcome Collection.

    36/258 (page 14)
    J4 . pulvinus were as sensitive as the lower. The two halves would thus have acted like opposing muscles, preventing all movement. Paradoxical as it may appear, this ‘ sensitive- ness ’ of Mimosa depends on the fact that one half of its motile organ is comparatively inactive. It is as if in our human illustration we had tied a strong man to a weakling ; the response of the former would then have been manifested to all eyes. In the young stem of ordinary plants the tissue is almost equally sensitive all round, so that a contractile movement of one side is counteracted by that of the dia- metrically opposite side. Consequently, when symmetrically stimulated, the stem does not respond by bending to one side or the other. The whole length, however, undergoes a con- traction and shortening, but to so slight an extent as to be imperceptible. This contraction of ordinary plants may, however, be recorded by means of a Magnifying Recorder. The response of the ordinary stem is then found to be essen- tially similar to that of the sensitive Mimosa, though less pronounced. The Writhing of a Tendril The following is a striking experiment demonstrating the sensitiveness of ordinary plants. A tendril which has twined round a support is cut off and freed from the sup- port. It appears to be altogether insensitive; but on sending a strong electric shock through it, the spiral tendril begins at once to uncurl and exhibit violent contortions, like the writhings of a worm under torture. The explanation of this extraordinary phenomenon is as follows : the tendril, when it touches a twig, coils, as every one knows, around the support. The inner surface of the spiral becomes toughened by constant friction, while the outer side of the spiral remains relatively more sensitive. The outer or convex side of the tendril is, in fact, like the lower half of the pulvinus, and exerts a predominant contraction under excitation. The greater contraction of the convex side on electrical stimulation causes the un- curling of the tendril. Experiments such as these prove that the distinction hitherto made between ‘ sensitive ’