166 DKOSERA ROTUNDIFOLIA. CHAP. VII, 



absorbed only m 7^0000 of a g ra i n > or '00000328 mg. ; and this 

 excessively minute amount sufficed to cause all the tentaclea 

 bearing these glands to be greatly inflected. The blade was also 

 inflected. 



Summary of the Results with Phosphate of Ammonia. 

 The glands of the disc, when excited by a half-minim 

 drop (-0296 nil.), containing -g-gVo f a grain (-0109 

 mg.) of this salt, transmit a motor impulse to the 

 exterior tentacles, causing them to bend inwards. A 

 minute drop, containing ,-3-^7^0 of a grain (-000423 

 mg.), if held for a few seconds in contact with a 

 gland, causes the tentacle bearing this gland to be 

 inflected. If a leaf is left immersed for a few hours, 

 and sometimes for a shorter time, in a solution so 

 weak that each gland can absorb only the ., 97ti ' OOU o 

 of a grain (-00000328 mg.), this is enough to excite 

 the tentacle into movement, so that it becomes 

 closely inflected, as does sometimes the blade. In 

 the general summary to this chapter a few remarks 

 will be added, showing that the efficiency of such 

 extremely minute doses is not so incredible as it 

 must at first appear. 



Sulphate of Ammonia. The few trials made with this and the 

 following five salts of ammonia were undertaken merely to 

 ascertain whether they induced inflection. Half-minims of a 

 solution of one part of the sulphate of ammonia to 437 of 

 water were placed on the discs of seven leaves, so that each 

 received 9^ of a grain, or '0675 mg. After 1 hr. the tentacles 

 of five of them, as well as the blade of one, were strongly 

 inflected. The leaves were not afterwards observed. 



Citrate of Ammonia. Half-minims of a solution of one part 

 to 437 of water were placed on the discs of six leaves. In 

 1 hr. the short outer tentacles round the discs were a little 

 inflected, with the glands on the discs blackened. After 

 3 hrs. 25 m. one leaf had its blade inflected, but none of the 

 exterior tentacles. All six leaves remained in nearly the same 

 state during the day, the submarginal tentacles, however, 



