144 DROSERA ROTUNDIFOLIA Cuap. VIL 
rele of a grain (:00445 mg.). Nevertheless, m two trials all 
the glands were plainly blackened ; in one case all three tcntacles 
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 zsh of a grain (°00387 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 zzigp 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 (8°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 43875 of water, and the glands were all 
blackened in 81m. 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 535 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 
goiutions are important, as they show that all the glands absorbed 
tno carbonate within the same time, which fact indeed there 
was not the least reason to doubt. So again, whenever all the 
