156 DKOSEJRA ROTUNDIFOLIA. Chap. VII. 



In this latter case each gland could have received only the 

 ^^^^QQ (or -000563 mg.) of a grain. Lastly, similar drops of a 

 solution of one part to 1750 of water (1 gr. to 4 oz.) were tried on 

 five leaves ; a drop being applied to four glands on the same 

 leaf. The tentacles on three of these leaves were not in the 

 least affected ; on the fourth leaf, two became inflected ; whilst 

 on the fifth, which happened to be a very sensitive one, all four 

 tentacles were plainly inflected in 6 hrs. 15 m. ; but only one re- 

 mained inflected after 21 hrs. I should, however, state that in 

 this case an unusually large drop adhered to the head of the 

 pin. Each of these glands could have received very little more 

 than issVoo of ^ gi'ain (or -000423); but this small quantity 

 sufficed to cause inflection. We must bear in mind that these 

 drops were applied to the viscid secretion for only from 10 to 

 15 seconds, and we have good reason to believe that all the 

 phosphate in the solution would not be diffused and absorbed in 

 this time. We have seen under the same circumstances that the 

 absorption by a gland of yg-^ of a grain of the carbonate, and 

 of "sYWo of ^ gi'ain of the nitrate, did not cause the tentacle bear- 

 ing the gland in question to be inflected ; so that here again the 

 phosj)hate is much more powerful than the other two salts. 



We will now turn to the 106 experiments with immersed 

 leaves. Having ascertained by repeated trials that moderately 

 strong solutions were highly efficient, I commenced with sixteen 

 leaves, each placed in tliirty minims of a solution of one part 

 to 43,750 of water (1 gr. to 100 oz.) ; so that each received 

 T^oo of a grain, or '04058 mg. Of these leaves, eleven had 

 nearly all or a great number of their tentacles inflected in 

 1 hr., and the twelfth leaf in 3 hrs. One of the eleven had 

 every single tentacle closely inflected in 50 m. Two leaves out 

 of the sixteen were only moderately affected, yet more so 

 than any of those simultaneously immersed in water ; and the 

 remaining two, which were pale leaves, were hardly at all 

 affected. Of the sixteen corresponding leaves in water, one 

 had nine tentacles, another six, and two others two tentacles 

 inflected, in the course of 5 hrs. So that the contrast in 

 appearance between the two lots was extremely great. 



Eighteen leaves .were immersed, each in thirty minims of a 

 solution of one part to 87,500 of water (1 gr. to 200 oz.), so 

 that each received 32V0 of a grain (-0202 mg.). Fourteen of 

 these were strongly inflected within 2 hrs., and some of them 

 within 15 m. ; three out of the eighteen were only slightly 

 affected, having twenty-one, nineteen, and twelve tentacles in- 



