Cuar. XL GENERAL SUMMARY. 271 
(00024 mg.) is sufficient to excite a single tentacle 
into movement. 
The nitrate of ammonia induces aggregation of the 
protoplasm much less quickly than the carbonate, but 
is more potent in causing inflection. A drop contain- 
ing g7oy Of a grain (027 mg.) placed on the disc acts 
powerfully on all the exterior tentacles, which have 
not themselves received any of the solution ; whereas a 
drop with z,';, of a grain caused only a few of these 
tentacles to bend, but affected rather more plainly the 
blade. A minute drop applied as before, and contain- 
ing zs4or Of a grain (0025 mg.), caused the tentacle 
bearing this gland to bend. By the immersion of 
whole leaves, it was proved that the absorption by a 
single gland of gaqeaa of a grain (0000987 mg.) was 
sufficient to set the same tentacle into movement. 
The phosphate of ammonia is much more powerful 
than the nitrate. A drop containing 5;;5 of a grain 
(0169 mg.) placed on the dise of a sensitive leaf 
causes most of the exterior tentacles to be inflected, 
as well as the blade of the leaf. A minute drop con- 
taining +ssso0 of a grain ("000423 mg.), applied for a 
few seconds to a gland, acts, as shown by the move- 
ment of the tentacle. When a leaf is immersed in 
thirty minims (1°7748 ml.) of a solution of one part by 
weight of the salt to 21,875,000 of water, the absorp- 
tion by a gland of only the z5s5000 Of a grain 
(00000328 mg.), that is, about the one-twenty-mil- 
lionth of a grain, is sufficient to cause the tentacle 
bearing this gland to bend to the centre of the 
leaf. In this experiment, owing to the presence of 
the water of crystallisation, less than the one-thirty- 
millionth of a grain of the efficient elements could 
have been absorbed. There is nothing remarkable in 
such minute quantities being absorbed by the glands, 
