138 DKOSERA EOTUNDIFOLIA. CllAP. ML 



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 

 watch-glasses, and thirty minims (1-775 ml.) 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 

 discoloured 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 tentacles. If we had no such evidence as 

 tliis, 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 tentacles ; but in this latter case 

 the exterior tentacles would not have become inflected until 

 some time had elapsed, instead of within half an hour, or even 

 within a few minutes, as usually occurred. All the glands on 

 the same leaf are of nearly the same size, as may best be seen 

 by cutting oif a narrow transverse strip, and laying it on its 

 side; hence theii* absorbing surfaces are nearly equal. The 

 long-headed glands on the extreme margin must be excepted, 

 as they are much longer than the others; but only the upper 

 surface is capable of absorption. Besides the glands, both 

 surfaces of the leaves and the pedicels of the tentacles bear 

 numerous minute papillae, which absorb carbonate of ammonia, 

 an infusion of raw meat, metallic salts, and probably many 

 other substances, but the absorption of matter by these papillae 

 never induces inflection. We must remember that the move- 

 ment of each separate tentacle depends on its gland being 

 excited, except when a motor impulse is transmitted from the 

 glands of the disc, and then the movement, as just stated, 

 does not take place until some little time has elapsed. I have 

 made these remarks because they show us that when a leaf is 

 immersed in a solution, and the tentacles are inflected, we can 

 judge with some accuracy how much of the salt each gland has 

 absorbed. For instance, if a leaf bearing 212 glands be immersed 

 in a measured quantity of a solution, containing ^^ of a grain of 

 a salt, and all the exterior tentacles, except twelve, are inflected, 

 we may feel sure that each of the 200 glands can on an average 

 have absorbed at most ayVo ^^ ^ grain of the salt. I say at 



