120 DROSERA ROTUNDIFOLIA. [Cuar. VII. 
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. 37 m. the glands 
became somewhat darker, and the cells beneath all of them now 
contained many spheres of aggregated protoplasm. This leaf received 
aig of a grain, and bore 166 glands. ach gland could, therefore, have 
received only y37¢s¢ of a grain (*000507 mg.) of the carbonate. 
‘wo other experiments are worth giving. A leaf was immersed 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 solution of one part to 5250 of 
water; and this excited welf-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 len:th equal to half or the whole of the glands. 
lt 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., during which time they were 
immersed in the solution; for the process of aggregation seems in- 
variably to snpervene 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, 
aud by the aggregation of the contents of their cells. The 
vapour is absorbed by the glands; these are blackened, and 
the tentacles are intiected. The glands of the disc, when 
excited by a half-minim drop (‘0296 c.c.), containing 51, of 
a grain (‘0675 mg.), transmit a motor impulse to the exterior 
tentacles, causing them to bend inwards. A minute drop, 
containing yz}, 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 immersed for a few 
hours in a solution, and a gland absorbs the +y+ryy of a grain 
(00048 mg.), its colour becomes darker, though not actually 
black; and the contents of the cells beneath the gland are 
plainly aggregated. Lastly, under the same circumstances, 
the absorption by a gland of the s¢soy of a grain (-00024 
mg.) suffices to excite the tentacle bearing this gland into 
movement. 
NITRATE OF AMMONIA. 
With this salt I attended only to the inflection of the leaves, for it is 
far less efficient than the carbonate in causing aggregation, although 
considerably more potent in causing inflection. I experimented with 
