Page:Researches on Irritability of Plants.djvu/111

 dots. It will be seen that there is an abolition of excitability, stimuli which were formerly effective becoming now quite ineffective.

I next tried to find out whether it were possible to restore the lost excitability by artificial means. Guided by the consideration that glycerin has the power of abstracting water, I applied a drop of strong glycerin to the pulvinus. It will be noted that this had the effect of quickly restoring the motile excitability of the pulvinus. The two responses



after the application of glycerin are practically similar to the normal responses at the beginning of the series. I am unable to say whether the restoration of excitability was here due entirely to the abstraction of water. One might think that continuous abstraction of water would induce a continuous variation of excitability—probably an enhancement reaching a maximum followed by a decline. I find, however, that the application of glycerin restores the normal excitability, and that generally speaking this remains constant even under the continued action of the reagent. This is a fortunate circumstance for those particular investi-