Cuap. VII.) PHOSPHATE OF AMMONTA. 125 
unaffected. Hence, the gzbq of a grain given to a sensitive leaf during 
warm weather perhaps produces a slight effect; but we must bear in 
mind that occasionally water causes as great an amount ot inflectiin 
as occurred in this last experiment. 
Summary of the Results with Nitrate of Ammonia.—The 
lands of the disc, when excited by a half-minim drop 
208 c.c.), containing gyy, of a grain of the nitrate 
027 mg.), transmit a motor impulse to the extcrior tentacles, 
causing them to bend inwards. A minute drop, containing 
pekoo Of a grain (‘00225 mg.), if held for a few seconds in 
ccntact with a gland, causes the tentacle bearing this gland 
to be inflected. If a leaf is left immersed for a few hours, 
and sometimes for only a few minutes, in a solution of such 
strength that each gland can absorb only the gyyyqz of a 
grain (0000937 mg.), this small amount is enough to excite 
each tentacle into movement, and it becomes closely in- 
flected. 
PuosrpHaTe OF AMMONIA. 
This salt is more powerful than the nitrate, even in a 
greater degree than the nitrate is more powerful than the car- 
bonate. This is shown by weaker solutions of the phosphate 
acting when dropped on the discs, or applied to the glands of 
the exterior tentacles, or when leaves are immersed. The 
difference in the power of these three salts, as tried in three 
different ways, supports the results presently to be given, 
which are so surprising that their credibility requires every 
kind of support. In 18721 experimented on twelve immersed 
leaves, giving each only ten minims of a solution: but this 
was a bad method, for so small a quantity hardly covered 
them. None of these experiments will, therefore, be given, 
though they indicate that excessively minute doses are 
efficient. When I read over my notes, in 1873, I entirely 
disbelieved them, and determined to make another set of 
experiments with scrupulous care, on the same plan as those 
made with the nitrate; namely by placing leaves in watch 
glasses, and pouring over each thirty minims of the solution 
under trial, treating at the same time and in the same 
manner other leaves with the distilled water used in making 
the solutions. During 1873, seventy-one leaves were thus 
tried in solutions of various strengths, and the same number 
