inflected after an interval 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 1/19200 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 1/14400 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 inflection, 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 1/320 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 solutions 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 the [page 145] tentacles become inflected within the same time, we have evidence, as before remarked, of simultaneous absorption.  I did not count the number of glands on these four leaves; but as they were fine ones, and as we know that the average number of glands on thirty-one leaves was 192, we may safely assume that each bore on an average at least 170; and if so, each blackened gland could have absorbed only 1/54400 of a grain (.00119 mg.) of the carbonate.