Cuar. VIL] PHOSPHATE OF AMMONIA. 127 
part of the phosphate to 875 of water, was applied to the secretion on 
three glands, each of which thus received only 57155 of a grain (00112 
mg.), and all three tentacles became inflected. Similar 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 +750 (or *000563 mg.) of a 
grain. Lastly, similar drops of a solution of one part to 1750 of 
water (1 gr. to 4 0z.) 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 remained inflected 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 753500 
of a grain (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 5455 of a grain of the 
carbonate, and of 5715y of a 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 109 
02.); so that each received z,55 of a grain, or *04058 mg. Of these 
leaves, eleven had nearly ali 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 corre- 
sponding 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 
gio Of a grain ('0202 mg.). Fourteen of these were strongly 
inflected within 2 hrs., and some of them within 15 m.; three out of 
