Cuar. VIL. CARBONATE OF AMMONIA. 147 
safely assume that there were at least 140; and if so, each 
gland could have received only the zy2ig5 Of @ grain, or 
“00048 mg. 
A weaker solution was then made of one part to 7000 of water, 
and four leaves were immersed in it; but I will give only one 
case. A leaf was placed in ten minims of this solution; after 
1 hr. 87 m. the glands became somewhat darker, and the cells 
beneath all of them now contained many spheres of aggregated 
protoplasm. This leaf received 73, of a grain, aud bore 166 
glands. Each gland could, therefore, have received only y37es5 
of a grain (000507 mg.) of the carbonate. 
Two other experiments are worth giving. A leaf was im- 
mersed for 4 hrs. 15 m. in distilled water, and there was no 
aggregation; it was then placed for 1 hr. 15 m. in a little solu- 
tion of one part to 5250 of water; and this excited well-marked 
aggregation and inflection. Another leaf, after having been 
immersed for 21 hrs. 15 m. in distilled water, had its glands 
blackened, but there was no aggregation in the cells beneath 
them; it was then left in six minims of the same solution, and 
in 1 hr. there was much aggregation in many of the tentacles; 
in 2 hrs. all the tentacles (146 in number) were affected—the 
aggregation extending down for a length equal to half or the 
whole of the glands. It is extremely improbable that these two 
leaves would have undergone aggregation if they had been left 
for a little longer in the water, namely for 1 hr. and 1 hr. 15 m., 
curing which time they were immersed in the solution; for the 
process of aggregation seems invariably to supervene slowly and 
very gradually in water. 
Summary of the Results with Carbonate of Ammonia.— 
The roots absorb the solution, as shown by their changed 
colour, and by the aggregation of the contents of their 
cells. The vapour is absorbed by the glands; these 
are blackened, and the tentacles are inflected. The 
glands of the disc, when excited by a half-minim drop 
(0296 ml.), containing ,}; of a grain (0675 mg.), 
transmit a motor impulse to the exterior tentacles, 
causing them to bend inwards. A minute drop, con- 
taining z;155 of a grain (00445 mg.), if held for a 
few seconds in contact with a gland, soon causes the 
tentacle bearing it to be inflected. If a leaf is left 
