Page:Researches on Irritability of Plants.djvu/119

96 dioxide, on the other hand, is extremely poisonous. Introduction of this gas was attended by an immediate excitatory fall, which was repeated twice. After this the plant became perfectly insensitive (fig. 55); the gas had in reality killed it.

Equally fatal is the effect of sulphur dioxide. Introduction of the gas was attended by an immediate excitatory

fall of the leaf, after which it became quite insensitive (fig. 56). Restoration of fresh air did not revive the plant, which succumbed completely to the toxic action of the gas.

There is in general a temporary depression of excitability in Mimosa under sudden diminution of intensity of light.

Absorption of water induces a depression or abolition