Chap.VIL] salts op AMMONIA. HI 



CHAPTER VII. 



THE EFFECTS OF SALTS OF AMMONIA. 



Manner of performing the experiments Action of distilled water in com- 

 parison with the solutions Carbonate of ammonia, absorbed by the 

 roots The vapour absorbed by the glands Drops on the disc Minute 

 drops applied to si-paratc glands Leaves immersed in weak solutions 

 Minuteness of the doses which induce aggregation of the protoplasm 

 Nitrate of ammonia, analogous experiments with Phosphate of 

 ammonia, analogous experiments with Other salts of ammoniac-Sum- 

 mary and concluding remarks on the action of the salts of ammonia. 



The chief object in this chapter is to show how powerfully 

 the salts of ammonia act on the leaves of Drosera, and more 

 especially to show what an extraordinarily small quantity 

 suffices to excite inflection. I shall therefore be compelled 

 to enter into full details. Doubly distilled water was always 

 used; and for the more delicate experiments, water which 

 had been prepared with the utmost possible care was given 

 me by Professor Frankland. The graduated measures were 

 tested, and found as accurate as such measures can be. The 

 salts were carefully weighed, and in all the more delicate 

 experiments, by Borda's double method. But extreme ac- 

 curacy would have been superfluous, as the leaves differ great- 

 ly in irritability, according to age, condition, and constitu- 

 tion. Even the tentacles on the same leaf differ in irrita- 

 bility to a marked decree. My experiments were tried in 

 the following several ways. 



Firstly. Drops which were ascertained by repeated trials to be 

 on an average about half a minim, or the -i>^p of a fluid ounce 

 (.0296 CO.), were placed by the same pointecl instrument on the 

 discs of the leaves, and the inflection of the exterior rows of tenta- 

 cles observed at successive intervals of time. It was first ascer- 

 tained, from between thirty and forty trials, that distille<l water 

 dropped in this manner produces no efTect, except that sometimes, 

 though rarely, two or three tentacles become inflected. In fact all 

 the many trials with solutions which were so weak as to produce 

 no efTect lead to the same result that water is ineflTicient. 



Secondly. The hesid of a small pin, fixed into a handle, waa 

 dipped into the solution under trial. The small drop which ad- 



