148 DROSERA EOTUNDIFOLIA. Chap. VII. 



immersed for a few hours in a solution, and a gland 

 absorbs the ttAito 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 circumstances, 

 the absorption by a gland of the ^ ^ ^\ „ „ of a grain 

 (•00024 mg.) suffices to excite the tentacle bearing this 

 o-land into movement. 



Nitrate of Ammonia. 



With the salt I attended only to the inflection of the leaves, 

 for it is far less efficient than the carbonate in causing aggrega- 

 tion, although considerably more potent in causing inflection. I 

 experimented with half-minims ('0296 ml.) on the discs of fifty- 

 two leaves, but will give only a few cases. A solution of one 

 part to 109 of water was too strong, causing httle inflection, and 

 after 21 hrs. killing, or nearly killing, four out of six leaves 

 which were thus tried ; each of which received the g-i ^ of a grain 

 (or '27 mg.). A solution of one part to 218 of water acted most 

 energetically, causing not only the tentacles of all the leaves, 

 but the blades of some, to be strongly inflected. Fourteen 

 leaves were tried with drops of a solution of one part to 875 

 of water, so that the disc of each received the ygVo of a grain 

 (•0337 mg.). Of these leaves, seven were very strongly acted on, 

 the edges being generally inflected ; two were moderately acted 

 on ; and five not at all. I subsequently tried three of these latter 

 five leaves with urine, saliva, and mucus, but they were only 

 slightly afi'ected ; and this proves that they were not in an active 

 condition. I mention this fact to show how necessary it is to 

 experiment on several leaves. Two of the leaves, which were 

 well inflected, re-expanded after 51 hrs. 



In the following exi^eriment I happened to select very sensi- 

 tive leaves. Ilalf-minims of a solution of one part to 1094 of 

 water (i.e. 1 gr. to 2h oz.) were placed on the discs of nine leaves, 

 so that each received the 2T00 of a grain (027 mg.). Three of 

 them had their tentacles strongly inflected and their blades curled 

 inwards ; five were slightly and somewhat doubtfully affected, 

 having from three to eight of their exterior tentacles inflected : 

 one leaf was not at all affected, yet was afterwards acted on by 

 saliva. In six of these cases, a trace of action was perceptible in 



