Cuap. VIL] PHOSPHATE OF AMMONIA. 135 
blade became slightly bowed towards the footstalk, and so remained 
for 48 hrs. ‘The exterior tentacles, excepting those of the three or 
four outermost rows, were now also inflected to an unusual degree. 
(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 extremly weak solution acted on the more sensitive leaves ; 
each of which received only the oboy 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 -1005007 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 absorbed only 
ze7eooon 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. 
Summary of the Results with Phosphate of Ammonia.—The 
glands of the disc, when excited by a half-minim drop (‘0296 
c.c.), containing 545 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 x53000 
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. Ifa 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 y57¢yo00 Of a grain (00000328 
ing.), 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 minute doses is not so incredible as it must at first 
appear. 
