Page:Researches on Irritability of Plants.djvu/127

104 In order to discover how constant is the death-point, I repeated the experiment with numerous other specimens. We have seen that the pulvinated organs present in the leaves of Desmodium gyrans and the bean plant (Vicia Faba) exhibit responsive movement under excitation. In fig. 60 is depicted the death record taken under standard conditions with the leaf of Desmodium. The record was commenced at 35° C.; it is seen that thermo-mechanical inversion took place at 61° C.

The next figure (fig. 61) shows the record with the leaf of bean plant. Here the responsive movements are very large. The inversion is seen to take place at 60° C.

The occurrence of death-spasm may also be shown by means of ordinary plants. If we take a hollow tubular organ, such as the hollow leaf-stalk of gourd or hollow flower-stalk of any other plant, cut it in the form of a spiral and subject it to the rising temperature of the bath, there is noticed at first an expansive movement of uncurling of spiral. On reaching the death-point, however, the former movement is suddenly reversed to one of curling.

Flowers like French marigold exhibit death-spasm by sudden movement of opening or closure.

By employing the electric mode of investigation I