120 DROSERA ROTUNDIFOLIA. [Coap. VIL 



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. 37 m. 

 the glands became somewhat darker, and the cells beneath all 

 of them now contained many spheres of aggregated protoplasm. 

 This leaf received y^ of a grain, and bore IGti glands. Each gland 

 could, therefore, have received only n ^' ^gg of a grain (.000507 mg.) 

 of the carbonate. 



Two other experiments are worth giving. A leaf was immersed 

 for 4 hrs. 15 ra. 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 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 aggie- 

 gation in many of the tentacles; in 2 hrs. all the tentacles (146 in 

 number) were afTected 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 aggrega- 

 tion 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 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 col- 

 our, 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 c.c), containing fiv of 

 a grain (.0675 mg.), transmit a motor impulse to the exterior 

 tentacles, causing them to bend inwards. A minute drop, 

 containing -rriinr 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 Trt'nnr 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 cir- 

 cumstances, the absorption by a gland of the wr^rez of a 

 grain (.00024 mg.) suflBces to excite the tentacle bearing this 

 gland into movement. 



NITRATE OF AMHONTA. 



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 ex- 



