twelve corresponding leaves in water, not one had its blade inflected;
after from 1 to 2 hrs. one had thirteen of its outer tentacles
inflected; a second six, and four others either one or two inflected.
After 8 hrs. the outer tentacles did not become more inflected; whereas
this occurred with the leaves in the solution. I record in my notes
that [page 158] after the 8 hrs. it was impossible to compare the two
lots, and doubt for an instant the power of the solution.
Two of the above leaves in the solution had all their tentacles, except
three and four, inflected within an hour. I counted their glands, and,
on the same principle as before, each gland on one leaf could have
absorbed only 1/1164800, and on the other leaf only 1/1472000, of a
grain of the phosphate.
Twenty leaves were immersed in the usual manner, each in thirty minims
of a solution of one part to 218,750 of water (1 gr. to 500 oz.). So
many leaves were tried because I was then under the false impression
that it was incredible that any weaker solution could produce an
effect. Each leaf received 1/8000 of a grain, or .0081 mg. The first
eight leaves which I tried both in the solution and in water were
either young and pale or too old; and the weather was not hot. They
were hardly at all affected; nevertheless, it would be unfair to
exclude them. I then waited until I got eight pairs of fine leaves, and
the weather was favourable; the temperature of the room where the
leaves were immersed varying from 75 to 81 (23 .8 to 27 .2 Cent.) In
another trial with four pairs (included in the above twenty pairs), the
temperature in my room was rather low, about 60 (15 .5 Cent.); but the
plants had been kept for several days in a very warm greenhouse and
thus rendered extremely sensitive. Special precautions were taken for
this set of experiments; a chemist weighed for me a grain in an
excellent balance; and fresh water, given me by Prof. Frankland, was
carefully measured. The leaves were selected from a large number of
plants in the following manner: the four finest were immersed in water,
and the next four finest in the solution, and so on till the twenty
pairs were complete. The water specimens were thus a little favoured,
but they did not undergo more inflection than in the previous cases,
comparatively with those in the solution.
Of the twenty leaves in the solution, eleven became inflected within 40
m.; eight of them plainly and three rather doubtfully; but the latter
139