With respect to the following experiments, I must premise that the leaves, both those placed in the solutions and in water, were taken from plants which had been kept in a very warm greenhouse during the winter. They were thus rendered extremely sensitive, as was shown by water exciting them much more than in the previous experiments. Before giving my observations, it may be well to remind the reader that, judging from thirty-one fine leaves, the average number of tentacles is 192, and that the outer or exterior ones, the movements of which are alone significant, are to the short ones on the disc in the proportion of about sixteen to nine. [page 161]
Four leaves were immersed as before, each in thirty minims of a solution of one part to 328,125 of water (1 gr. to 750 oz.). Each leaf thus received 1/12000 of a grain (.0054 mg.) of the salt; and all four were greatly inflected.
(1) After 1 hr. all the outer tentacles but one inflected, and the blade greatly so; after 7 hrs. began to re-expand.
(2) After 1 hr. all the outer tentacles but eight inflected; after 12 hrs. all re-expanded.
(3) After 1 hr. much inflection; after 2 hrs. 30 m. all the tentacles but thirty-six inflected; after 6 hrs. all but twenty-two inflected; after 12 hrs. partly re-expanded.
(4) After 1 hr. all the tentacles but thirty-two inflected; after 2 hrs. 30 m. all but twenty-one inflected; after 6 hrs. almost re-expanded.
Of the four corresponding leaves in water:—
(1) After 1 hr. forty-five tentacles inflected; but after 7 hrs. so many had re-expanded that only ten remained much inflected.
(2) After 1 hr. seven tentacles inflected; these were almost re-expanded in 6 hrs.
(3) and (4) Not affected, except that, as usual, after 11 hrs. the short tentacles on the borders of the disc formed a ring.