Chap. VII.] CARBONATE OP AMMONIA. 117 



We will now turn to the effects of solutions of the carbonate. 

 Half-minims of a solution of one part to 437 of water were placed 

 on the discs of twelve leaves; so that each received g^g of a grain 

 or .0675 mg. Ten of these had their exterior tentacles well in- 

 flected; the blades of some being also much curved inwards. In 

 two cases several of the exterior tentacles were inflected in 35 m.; 

 but the movement was generally slower. These ten leaves re- 

 expanded in periotls varying between 21 hrs. and 45 hrs., but in 

 one case not until 67 hrs. had elapsed; so that they re-expanded 

 much more quickly than leaves which have caught insects. 



The same-sized drops of a solution of one part to 875 of water 

 were placed on the discs of eleven leaves; six remained quite un- 

 affected, whilst five had from three to six or eight of their exterior 

 tentacles inflected; but this degree of movement can hardly be 

 considered as trustworthy. Each of these leaves received yg^ir of a 

 grain (.0337 mg.), distributed between the glands of the disc, but 

 this was too small an amount to produce any decided effect on the 

 exterior tentacles, the glands of which had not themselves received 

 any of the salt. 



Minute drops on the head of a small pin, of a solution of one 

 part of the carbonate to 218 of water, were next tried in the man- 

 ner above described. A drop of this kind equals on an average ^ 

 of a minim, and therefore contains j-g^-g- of a grain (.0135 mg.) of 

 the carbonate. I touched with it the viscid secretion round three 

 glands, so that each gland received only uioo of a grain (.00445 

 mg). Nevertheless, in two trials all the glands were plainly black- 

 ened ; in one case all three tentacles were well inflected after an in- 

 terval of 2 hrs. 40 m. ; and in another case two of the three tentacles 

 were inflected. I then tried drops of a weaker solution of one part 

 to 292 of water on twenty-four glands, always touching the viscid 

 secretion round three glands with the same little drop. Each gland 

 thus received only the -rgimr of a grain (.00337 mg.), yet some of 

 them were a little darkened; but in no one instance were any of 

 the tentacles inflected, though they were watched for 12 hrs. 

 When a still weaker solution (viz. one part to 437 of water) was 

 tried on six glands, no effect whatever was perceptible. We thus 

 learn that the -j-riinr of a grain (.00445 mg.) of carbonate of am- 

 monia, if absorbed by a gland, suffices to induce inflection in the 

 basal part of the same tentacle; but as already stated, I was able 

 to hold with a steady hand the minute drops in contact with the 

 secretion only for a few seconds; and if more time had been allowed 

 for diffusion and absorption, a much weaker solution would cer- 

 tainly have acted. 



Some experiments were made by immersing cut-off leaves in 

 solutions of different strengths. Thus four leaves were left for 

 about 3 hrs. each in a drachm (3.549 c.c.) of a solution of one part 

 of the carbonate to 5250 of water; two of these had almost every 

 tentacle inflected, the third had about half the tentacles and the 

 fourth about one-third inflected ; and all the glands were blackened. 

 Another leaf was place<I in the same quantity of a solution of one 

 part to 7000 of water, and in 1 hr. 10 m. every single tentacle was 



