Chap. VII. EFFECTS OF WATER. 139 



most, for the papillfe will have absorbed some small amount, 

 and so will perhaps the glands of the twelve excluded tentacles 

 which did not become inflected. The application of this prin- 

 ciple leads to remarkable conclusions with respect to the 

 minuteness of the doses causing inflection. 



On the Action of Distilled Water in causing Inflection. 



Although in all the more important experiments the dif- 

 ference between the leaves simultaneously immersed in water 

 and in the several solutions will be described, nevertheless it 

 may be well here to give a summary of the effects of water. 

 The fact, moreover, of pure water acting on the glands deserves 

 in itself some notice. Leaves to the number of 111 were im- 

 mersed in water at the same time with those in the solutions, 

 and their state recorded at short intervals of time. Thirty-two 

 other leaves were separately observed in water, making alto- 

 gether 173 experiments. Many scores of leaves were also im- 

 mersed in water at other times, but no exact record of the 

 effects produced was kept ; yet these cursory observations sup- 

 port the conclusions arrived at in this chapter. A few of the 

 long-headed tentacles, namely from one to about six, were 

 commonly inflected within half an hour after immersion ; as 

 were occasionally a few, and rarely a considerable number of 

 the exterior round-headed tentacles. After an immersion of 

 from 5 to 8 hrs. the short tentacles surrounding the outer 

 parts of the disc generally become inflected, so that their glands 

 form a small dark ring on the disc; the exterior tentacles 

 not partaking of this movement. Hence, excepting in a few 

 cases hereafter to be specified, we can judge whether a solution 

 produces any effect only by observing the exterior tentacles 

 within the first 3 or 4 hrs. after immersion. 



Now for a summary of the state of the 173 leaves after an 

 immersion of 3 or 4 hrs. in pure water. One leaf had almost 

 all its tentacles inflected ; three leaves had most of them sub- 

 inflected; and thirteen had on an average 36'5 tentacles in- 

 flected. Thus seventeen leaves out of the 173 were acted on in 

 a marked manner. Eighteen leaves had from seven to nineteen 

 tentacles inflected, the average being 9*3 tentacles for each 

 leaf. Forty-four leaves had from one to six tentacles inflected, 

 generally the long-headed ones. So that altogether of the 173 

 leaves carefully observed, seventy-nine were affected by the 

 water in some degree, though commonly to a very slight degree; 

 and ninety-four were not affected in the least degree. This 



