A leaf was then immersed in twenty minims of a solution of one part to 4375 of water, so that it received 1/240 of a grain (.27 mg.); in 5 m. there was a slight change of colour in the glands, and in 15 m. small spheres of protoplasm were formed in the cells beneath the glands of all the tentacles. In these cases there could not be a shadow of a doubt about the action of the solution.
A solution was then made of one part to 5250 of water, and I experimented on fourteen leaves, but will give only a few of the cases. Eight young leaves were selected and examined with care, and they showed no trace of aggregation. Four of these were placed in a drachm (3.549 ml.) of distilled water; and four in a similar vessel, with a drachm of the solution. After a time the leaves were examined under a high power, being taken alternately from the solution and the water. The first leaf was taken out of the solution after an immersion of 2 hrs. 40 m., and the last leaf out of the water after 3 hrs. 50 m.; the examination lasting for 1 hr. 40 m. In the four leaves out of the water there was no trace of aggregation except in one specimen, in which a very few, extremely minute spheres of protoplasm were present beneath some of the round glands. All the glands were translucent and red. The four leaves which had been immersed in the solution, besides being inflected, presented a widely different appearance; for the contents of the cells of every single tentacle on all four leaves were conspicuously aggregated; the spheres and elongated masses of protoplasm in many cases extending halfway down the tentacles. All the glands, both those of the central and exterior tentacles, were opaque and blackened; and this shows that all had absorbed some of the carbonate. These four leaves were of very nearly the same size, and the glands were counted on one and found to be 167. This being the case, and the four leaves having been immersed in a drachm of the solution, each gland could have received on an average only 1/64128 of a grain (.001009 mg.) of the salt; and this quantity sufficed to induce within a short time conspicuous aggregation in the cells beneath all the glands.
A vigorous but rather small red leaf was placed in six minims of the same solution (viz. one part to 5250 of water), so that it received 1/960 of a grain (.0675 mg.). In 40 m. the glands appeared rather darker; and in 1 hr. from four to six spheres of protoplasm were formed in the cells beneath the glands of all the tentacles. I did not count the tentacles, but we may [page 147] safely assume that there were at least 140; and if so, each gland could have received only the 1/134400 of a grain, or .00048 mg.
A weaker solution was then made of one part to 7000 of water, and four leaves were immersed in it; but I will give only one case. A leaf was placed in ten minims of this solution; after 1 hr. 37 m. the glands became somewhat darker, and the cells beneath all of them now contained many spheres of aggregated protoplasm. This leaf received 1/768 of a grain, and bore 166 glands. Each gland could, therefore, have received only 1/127488 of a grain (.00507 mg.) of the carbonate.
Two other experiments are worth giving. A leaf was immersed for 4 hrs. 15 m. in distilled water, and there was no aggregation; it was then placed for 1 hr. 15 m. in a little solution of one part to 5250 of water; and this excited well-marked aggregation and inflection. Another leaf, after having been immersed for 21 hrs. 15 m. in distilled water, had its glands blackened, but there was no aggregation in the cells beneath them; it was then left in six minims of the same solution, and in 1 hr. there was much aggregation in many of the tentacles; in 2 hrs. all the tentacles (146 in number) were affected--the aggregation extending down for a length equal to half or the whole of the glands. It is extremely improbable that these two leaves would have undergone aggregation if they had been left for a little longer in the water, namely for 1 hr. and 1 hr. 15 m., during which time they were immersed in the solution; for the process of aggregation seems invariably to supervene slowly and very gradually in water.]
Summary of the Results with Carbonate of Ammonia.--The roots absorb the solution, as shown by their changed colour, and by the aggregation of the contents of their cells.