(2) to (8) These leaves, after 2 hrs. 40 m., had respectively 42, 12,
9, 8, 2, 1, and 0 tentacles inflected, which all re-expanded within 24
hrs., and most of them within a much shorter time.
When the two lots of eight leaves in the solution and in the water were
compared after the lapse of 24 hrs., they undoubtedly differed much in
appearance. The few tentacles on the leaves in water which were
inflected had after this interval re-expanded, with the exception of
one leaf; and this presented the very unusual case of the blade being
somewhat inflected, though in a degree hardly approaching that of the
two leaves in the solution. Of these latter leaves, No. 1 had almost
all its tentacles, together with its blade, inflected after an
immersion of 2 hrs. 30 m. Leaves No. 2 and 3 were affected at a much
slower rate; but after from 24 hrs. to 48 hrs. almost all their
tentacles were closely inflected, and the blade of one quite doubled
up. We must therefore admit, incredible as the fact may at first
appear, that this extremely weak solution acted on the more sensitive
leaves; each of which received only the 1/80000 of a grain (.00081 mg.)
of the phosphate. Now, leaf No. 3 bore 178 tentacles, and subtracting
the three which were not inflected, each gland could have absorbed only
the 1/14000000 of a grain, or .00000463 mg. Leaf No. 1, which was
strongly acted on within 2 hrs. 30 m., and had all its outer tentacles,
except thirteen, inflected within 6 hrs. 30 m., bore 260 tentacles; and
on the same principle as before, each gland could have [page 166]
absorbed only 1/19760000 of a grain, or .00000328 mg.; and this
excessively minute amount sufficed to cause all the tentacles bearing
these glands to be greatly inflected. The blade was also inflected.]
A Summary of the Results with Phosphate of Ammonia. The glands of the
disc, when excited by a half-minim drop (.0296 ml.), containing 1/3840
of a grain (.0169 mg.) of this salt, transmit a motor impulse to the
exterior tentacles, causing them to bend inwards. A minute drop,
containing 1/153600 of a grain (.000423 mg.), if held for a few seconds
in contact with a gland, causes the tentacle bearing this gland to be
inflected. If a leaf is left immersed for a few hours, and sometimes
for a shorter time, in a solution so weak that each gland can absorb
only the 1/9760000 of a grain (.00000328 mg.), this is enough to excite
the tentacle into movement, so that it becomes closely inflected, as
does sometimes the blade. In the general summary to this chapter a few
remarks will be added, showing that the efficiency of such extremely
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