150 DROSEKA EOTUNDIFOLIA. Chap. VII. 



Having made some preliminary trials as a guide, five leaves 

 were placed in the same little vessel in thirty minims of a solu- 

 tion of one part of the nitrate to 7875 of water (1 gr. to 18 oz.); 

 and this amount of fluid just sufficed to cover them. After 

 2 hrs. 10 m. three of the leaves were considerably inflected, and 

 the other two moderately. The glands of all became of so dark 

 a red as almost to deserve to be called black. After 8 hrs. four 

 of the leaves had all their tentacles more or less inflected ; whilst 

 the fifth, wliich I then perceived to be an old leaf, had only thirty 

 tentacles inflected. Next morning, after 23 hrs. 40 m., all the 

 leaves were in the same state, excepting that the old leaf had a 

 few more tentacles inflected. Five leaves which had been placed 

 at the same time in water were observed at the same intervals 

 of time ; after 2 hrs. 10 m. two of them had four, one had seven, 

 one had ten, of the long-headed marginal tentacles, and the 

 fifth had four round-headed tentacles, inflected. After 8 hrs. 

 there was no change in these leaves, and after 21 hrs. all the 

 marginal tentacles had re-expanded ; but in one leaf, a dozen, and 

 in a second leaf' half a dozen, submarginal tentacles had become 

 inflected. As the glands of the five leaves in the solution were 

 simultaneously darkened, no doubt they had all absorbed a nearly 

 equal amount of the salt : and as -^-^ of a grain was given to the 

 five leaves together, each got y^ of a grain (-015 mg.). I did 

 not count the tentacles on these leaves, which were moderately 

 fine ones, but as the average number on thii-ty-one leaves was 

 192, it would be safe to assume that each bore on an average at 

 least 160. If so, each of the darkened glands could have 

 received only y 3 oVoo ^^ ^ grain of the nitrate ; and this caused 

 the inflection of a great majority of the tentacles. 



This plan of immersing several leaves in the same vessel 

 is a bad one, as it is impossible to feel sure that the more 

 vigorous leaves do not rob the weaker ones of their share of 

 the salt. The glands, moreover, must often touch one another 

 or the sides of the vessel, and movement may have been thus 

 excited; but the corresponding leaves in water, which were 

 little inflected, though rather more so than commonly occurs, 

 were exposed in an almost equal degree to these same sources 

 of error. I will, therefore, give only one other experiment made 

 in this manner, though many were tried and all confirmed 

 the foregoing and following results. Four leaves were placed 

 in forty minims of a solution of one part to 10,500 of water; 

 and assuming that they absorbed equally, each leaf received 

 __i_ of a grain (-0562 mg.). After 1 hr. 20 m. many of the 

 tentacles ou all four leaves were somewhat inflected. After 



