112 DROSERA ROTUNDIFOLIA. [Chap. VIL 



hered to it, and which was much too small to fall off, was cautious- 

 ly placed, by the aid of a lens, in contact with the secretion sur- 

 ToundfnL; the glands of one, two, three, or four of the exterior tentar 

 clcs of the same leaf. Great care was taken that the glands them-^ 

 selves should not be touched. I had supposed that the drops were 

 of nearly the same size; but on trial this proved a great mistake. 

 I first measured some water, and removed 300 drops, touching the 

 pin's head each time on blotting-paper; and on again measuring 

 the water, a drop was found to equal on an average about the i^ 

 of a minim. Some water in a small vessel was weighed (and this 

 is a more accurate method ) , and 300 drops removed as before ; and 

 on again weighing the water, a drop was found to equal on an aver- 

 age only the ^ of a minim. I repeated the operation, but en- 

 deavoured this time, by taking the pin's head out of the water 

 obliquely and rather quickly, to remove as large drops as possible; 

 and the result showed that I had succeeded, for each drop on an 

 average equalled j-J^j of a minim. I repeated the operation in 

 exactly the same manner, and now the drops averaged g^ of a 

 minim. Bearing in mind that on these two latter occasions special 

 pains were taken to remove as large drops as possible, we may 

 safely conclude that the drops used in my experiments were at least 

 equal to the ^ of a minim, or .0029 c.c. One of these drops could 

 be applied to three or even four glands, and if the tentacles became 

 inflected, some of the solution must have been absorbed by all; 

 for drops of pure water, applied in the same manner, never produced 

 any effect. I was able to hold the drop in steady contact with 

 the secretion only for ten to fifteen seconds; and this was not time 

 enough for the diffusion of all the salt in solution, as was evi- 

 dent, from three or four tentacles treated successively with the 

 same drop, often becoming inflected. All the matter in solution 

 was even then probably not exhausted. 



Thirdly. Leaves were cut off and immersed in a measured 

 quantity of the solution under trial; the same number of leaves 

 being immersed at the same time, in the same quantity of the 

 distilled water which had been used in making the solution. The 

 leaves in the two lots were compared at short intervals of time, 

 up to 24 hrs., and sometimes to 48 hrs. They were immersed by 

 being laid as gently as possible in numbered watchglasses, and 

 thirty minims (1.776 c.c.) of the solution or of water was poured 

 over each. 



Some solutions, for instance that of carbonate of ammonia, 

 quickly discolour the glands; and as all on the same leaf were dis- 

 coIoure<l simultaneously, they must all have absorbed some of the 

 salt within the same short period of time. This was likewise shown 

 by the simultaneous inflection of the several exterior rows of ten- 

 tacles. If we had no such evidence as this, it might have been 

 supposed that only the glands of the exterior and inflected tentacles 

 had absorbed the salt; or that only those on the disc had absorbed 

 it, and had then transmitted a motor impulse to the exterior tenta- 

 cles; but in this latter case the exterior tentacles would not have 

 become inflected until some time had elapsed, instead of within 



