Chap. VII.] PHOSPHATE OF AMMONIA. 127 



one part of the phosphate to 875 of water, was applied to the secre- 

 tion on three glands, each of which thus received only rrhsv o^ * 

 grain (.00112 rag.), and all three tentacles became inllected. Sim- 

 ilar drops of a solution of one part to 1312 of water (1 gr. to 3 oz.) 

 were now tried on three leaves; a drop being applied to four glands 

 on the same leaf. On the first leaf three of the tentacles became 

 slightly inflected in 6 m., and re-expanded after 8 hrs. 45 m. On 

 the second, two tentacles became sub-inflected in 12 m. And on 

 the third all four tentacles were decidedly inflected in 12 m. ; they 

 remained so for 8 hrs. 30 m., but by the next morning were fully 

 re-expanded. In this latter case each gland could have received 

 only the -[- [^ o g (or .000563 mg.) of a grain. Lastly, similar drops 

 of a solution of one pari 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 alTected ; 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 remained in- 

 flected after 24 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 rs^Vifff of 

 a grain (or .000423); but this small quantity sufficed to cause in- 

 flection. 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 TriTro 9^ 

 a grain of the carbonate, and of ^-7-^ of ^ grain of the nitrate, 

 did not cause the tentacle bearing the gland in question to be 

 inflected; so that here again the phosphate 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 thirty minims of a solution of one part to 43,750 of 

 water (1 gr. to 100 oz.) ; so that each received ^^ 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 af- 

 fected, yet more so than any of those simultaneously immersed in 

 water; and the remaining two, which were pale leaves, were hard- 

 ly at all alTected. 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 appear- 

 ance 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 y,'o, of a grain (.0202 mg.). Fourteen of these were 

 strongly inflected within 2 hrs., and some of them within 15 m.; 



