(and this is a more accurate method), and 300 drops removed as before;
and on again weighing the water, a drop was found to equal on an
average only the 1/89 of a minim. I repeated the operation, but
endeavoured this time, by taking the pin s head out of the water
obliquely and rather quickly, to remove as large drops as possible; and
the result showed that I had succeeded, for each drop on an average
equalled 1/19.4 of a minim. I repeated the operation in exactly the
same manner, and now the drops averaged 1/23.5 of a minim. Bearing in
mind that on these two latter occasions special pains were taken to
remove as large drops as possible, we may safely conclude that the
drops used in my experiments were at least equal to the 1/20 of a
minim, or .0029 ml. One of these drops could be applied to three or
even four glands, and if the tentacles became inflected, some of the
solution must have been absorbed by all; for drops of pure water,
applied in the same manner, never produced any effect. I was able to
hold the drop in steady contact with the secretion only for ten to
fifteen seconds; and this was not time enough for the diffusion of all
the salt in solution, as was evident, from three or four tentacles
treated successively with the same drop, often becoming inflected. All
the matter in solution was even then probably not exhausted.
Thirdly. Leaves cut off and immersed in a measured [page 138] quantity
of the solution under trial; the same number of leaves being immersed
at the same time, in the same quantity of the distilled water which had
been used in making the solution. The leaves in the two lots were
compared at short intervals of time, up to 24 hrs., and sometimes to 48
hrs. They were immersed by being laid as gently as possible in numbered
watch-glasses, and thirty minims (1.775 ml.) of the solution or of
water was poured over each.
Some solutions, for instance that of carbonate of ammonia, quickly
discolour the glands; and as all on the same leaf were discoloured
simultaneously, they must all have absorbed some of the salt within the
same short period of time. This was likewise shown by the simultaneous
inflection of the several exterior rows of tentacles. If we had no such
evidence as this, it might have been supposed that only the glands of
the exterior and inflected tentacles had absorbed the salt; or that
only those on the disc had absorbed it, and had then transmitted a
motor impulse to the exterior tentacles; but in this latter case the
exterior tentacles would not have become inflected until some time had
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