141 DROSERA ROTUNDIFOLIA CHAP. V1L 



rr* ^ a S ra i n ('00445 mg.). Nevertheless, in two trials all 

 the glands were plainly blackened ; in one case all three tentacles 

 were well inflected after an interval of 2 hrs. 40 m. ; and in an- 

 other 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 19 ^ 00 of a grain ('00337 mg.), yet some of them were 

 a little darkened ; but in no one instance were any of the ten- 

 tacles 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 14 ^ 00 of a grain ('00445 mg.) of carbonate of ammonia, 

 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 certainly 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 ml.) 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 placed in the same quantity of a 

 solution of one part to 7000 of water, and in 1 hr. 16 m. every 

 single tentacle was well inflected, and all the glands blackened. 

 Six leaves were immersed, each in thirty minims (1'774 ml.) of 

 a solution of one part to 4375 of water, and the glands were all 

 blackened in 31 m. All six leaves exhibited some slight inflec- 

 tion, and one was strongly inflected. Four leaves were then 

 immersed in thirty minims of a solution of one part to 8750 of 

 water, so that each leaf received the ^^ of a grain ('2025 mg.). 

 Only one became strongly inflected ; but all the glands on all 

 the leaves were of so dark a red after one hour as almost to 

 deserve to be called black, whereas this did not occur with the 

 leaves which were at the same time immersed in water ; nor did 

 water produce this effect on any other occasion in nearly so 

 short a time as an hour. These cases of the simultaneous 

 darkening or blackening of the glands from the action of weak 

 sohitions are important, as they show that all the glands absorbed 

 the carbonate within the same time, which fact indeed there 

 was not the least reason to doubt. So again, whenever all tha 



