Page:Life Movements in Plants.djvu/72

42 In the pulvinus of Mimosa pudica, the lower half is eighty times more excitable than the upper, and the fall of the leaf is due to the predominant contraction of the more excitable lower half.

A diminution of turgor takes place in the excited cells. Restoration of turgor brings about recovery of the leaf to its normal erect position. Independent experiments show that the fall of the leaf may be brought about by an artificial diminution of turgor, and the erection of the leaf by an increase of turgor.