Page:Researches on Irritability of Plants.djvu/143

120 .17 second. The identity of these values shows that the inertia of the recorder has but little effect on the results obtained.

The latent period in any given specimen of the pulvinus of Mimosa is, as we have seen, under uniform conditions extremely constant. It differs, however, in different specimens and from season to season. A thin specimen has in general a shorter latent period than one which is stouter. Perhaps this fact is illustrated, with a certain exaggeration, in the case of Neptunia, the leaf and pulvinus of which are comparatively thick. In any case, we have already seen

that in its responsive movements, relatively to Mimosa pudica, it is very sluggish. In order to determine the latent period I employed a slow vibrator, that is to say, one which vibrates with a frequency of 10 per second. It will be seen by reference to fig. 73 that the responsive movement began after the sixth dot, the latent period being thus .6 second, or six times the value of the average latent period in Mimosa.

With Mimosa pudica I have carried out more than a hundred different determinations, and give below a tabular statement of seventy of those values which occurred most frequently amongst these. Specimens giving a latent