glands, but no effect whatever was produced, except perhaps in one
instance.
Sixty-three leaves were immersed in solutions of various strengths;
other leaves being immersed at the same time in the same pure water
used in making the solutions. The results are so remarkable, though
less so than with phosphate of ammonia, that I must describe the
experiments in detail, but I will give only a few. In speaking of the
successive periods when inflection occurred, I always reckon from the
time of first immersion. [page 150]
Having made some preliminary trials as a guide, five leaves were placed
in the same little vessel in thirty minims of a solution of one part of
the nitrate to 7875 of water (1 gr. to 18 oz.); and this amount of
fluid just sufficed to cover them. After 2 hrs. 10 m. three of the
leaves were considerably inflected, and the other two moderately. The
glands of all became of so dark a red as almost to deserve to be called
black. After 8 hrs. four of the leaves had all their tentacles more or
less inflected; whilst the fifth, which I then perceived to be an old
leaf, had only thirty tentacles inflected. Next morning, after 23 hrs.
40 m., all the leaves were in the same state, excepting that the old
leaf had a few more tentacles inflected. Five leaves which had been
placed at the same time in water were observed at the same intervals of
time; after 2 hrs. 10 m. two of them had four, one had seven, one had
ten, of the long-headed marginal tentacles, and the fifth had four
round-headed tentacles, inflected. After 8 hrs. there was no change in
these leaves, and after 24 hrs. all the marginal tentacles had
re-expanded; but in one leaf, a dozen, and in a second leaf, half a
dozen, submarginal tentacles had become inflected. As the glands of the
five leaves in the solution were simultaneously darkened, no doubt they
had all absorbed a nearly equal amount of the salt: and as 1/288 of a
grain was given to the five leaves together, each got 1/1440 of a grain
(.045 mg.). I did not count the tentacles on these leaves, which were
moderately fine ones, but as the average number on thirty-one leaves
was 192, it would be safe to assume that each bore on an average at
least 160. If so, each of the darkened glands could have received only
1/230400 of a grain of the nitrate; and this caused the inflection of a
great majority of the tentacles.
This plan of immersing several leaves in the same vessel is a bad one,
131