as it is impossible to feel sure that the more vigorous leaves do not
rob the weaker ones of their share of the salt. The glands, moreover,
must often touch one another or the sides of the vessel, and movement
may have been thus excited; but the corresponding leaves in water,
which were little inflected, though rather more so than commonly
occurs, were exposed in an almost equal degree to these same sources of
error. I will, therefore, give only one other experiment made in this
manner, though many were tried and all confirmed the foregoing and
following results. Four leaves were placed in forty minims of a
solution of one part to 10,500 of water; and assuming that they
absorbed equally, each leaf received 1/1152 of a grain (.0562 mg.).
After 1 hr. 20 m. many of the tentacles on all four leaves were
somewhat inflected. After [page 151] 5 hrs. 30 m. two leaves had all
their tentacles inflected; a third leaf all except the extreme
marginals, which seemed old and torpid; and the fourth a large number.
After 21 hrs. every single tentacle, on all four leaves, was closely
inflected. Of the four leaves placed at the same time in water, one
had, after 5 hrs. 45 m., five marginal tentacles inflected; a second,
ten; a third, nine marginals and submarginals; and the fourth, twelve,
chiefly submarginals, inflected. After 21 hrs. all these marginal
tentacles re-expanded, but a few of the submarginals on two of the
leaves remained slightly curved inwards. The contrast was wonderfully
great between these four leaves in water and those in the solution, the
latter having every one of their tentacles closely inflected. Making
the moderate assumption that each of these leaves bore 160 tentacles,
each gland could have absorbed only 1/184320 of a grain (.000351 mg.).
This experiment was repeated on three leaves with the same relative
amount of the solution; and after 6 hrs. 15 m. all the tentacles except
nine, on all three leaves taken together, were closely inflected. In
this case the tentacles on each leaf were counted, and gave an average
of 162 per leaf.
The following experiments were tried during the summer of 1873, by
placing the leaves, each in a separate watch-glass and pouring over it
thirty minims (1.775 ml.) of the solution; other leaves being treated
in exactly the same manner with the doubly distilled water used in
making the solutions. The trials above given were made several years
before, and when I read over my notes, I could not believe in the
results; so I resolved to begin again with moderately strong solutions.
Six leaves were first immersed, each in thirty minims of a solution of
132