Page:Life Movements in Plants.djvu/272

242. response of palvinated and growing organs will be seen in the following tabular statement :

Specimen.

Latent period.

Apex-time.

1 Period of recovery.

Motile piilvinus of Mimosa U'l sec.

pudica. '■ Motile pulvinus of Neptunia 0*6 ,

oleracea. Growing bud of Crininn ... i TO ,,

!

3 sees. 160 „ 240 „

1 16 minutes.

60

7

The contraction in gro\\ing organs under stimulus is sometimes con-<iderable. Thus in the filamentous corona of Passijiora quadrangular is the contraction may be as much as 15 per cent, of the original length. This is not very different from the excit::itory reaction of the typicilly sen- sitive stamens of the Cynerece, which exhibits a contraction from 8 to 22 per cant.

In Mimosa the normal rasponse to direct stimulus is negative, the leaf undergoing a fall. But sub-tonic speci- mens exhibit a positive response with erection of the leaf. The action of the stimulus itself improves the tonic condi- tion, and the abnormal positive is thus converted into normal negative, through diphasic response (p. 147). Simi- larly in growing organs, while the normal effect of sti- mulus is incipient contraction and retardation of growth under condition of sub-tonicity the response is by accele- ration of growth. Continuous stimulation converts this