136 DROSERA ROTUNDIFOLIA. Cuar. VIL 
CHAPTER VII. 
Tue Errects ofr Satts or AMMONIA. 
Manner of performing the experiments — Action of distilled water in 
comparison with the solutions —Carbonate of ammonia, absorbed 
by the roots — The vapour absorbed by the glands — Drops on the 
disc — Minute drops applied to separate glands — Leaves im- 
mersed 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 ammonia—-Summary and concluding re- 
marks on the action of the salts of ammonia. 
THE chief object in this chapter is to show how power- 
fully 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 accuracy would have been 
superfluous, as the leaves differ greatly in irritability, 
according to age, condition, and constitution. Even 
the tentacles on the same leaf differ in irritability 
to a marked degree. 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 54, of a fluid ounce 
(0296 ml.), were placed by the same pointed instrument on the 
