tentacles were decidedly inflected in 12 m.; they remained so for 8
hrs. 30 m., but by the next morning were fully re-expanded. [page 156]
In this latter case each gland could have received only the 1/115200
(or .000563 mg.) of a grain. Lastly, similar drops of a solution of one
part to 1750 of water (1 gr. to 4 oz.) were tried on five leaves; a
drop being applied to four glands on the same leaf. The tentacles on
three of these leaves were not in the least affected; on the fourth
leaf, two became inflected; whilst on the fifth, which happened to be a
very sensitive one, all four tentacles were plainly inflected in 6 hrs.
15m.; but only one remained inflected after 24 hrs. I should, however,
state that in this case an unusually large drop adhered to the head of
the pin. Each of these glands could have received very little more than
1/153600 of a grain (or .000423); but this small quantity sufficed to
cause inflection. We must bear in mind that these drops were applied to
the viscid secretion for only from 10 to 15 seconds, and we have good
reason to believe that all the phosphate in the solution would not be
diffused and absorbed in this time. We have seen under the same
circumstances that the absorption by a gland of 1/19200 of a grain of
the carbonate, and of 1/57600 of a grain of the nitrate, did not cause
the tentacle bearing the gland in question to be inflected; so that
here again the phosphate is much more powerful than the other two
salts.
We will now turn to the 106 experiments with immersed leaves. Having
ascertained by repeated trials that moderately strong solutions were
highly efficient, I commenced with sixteen leaves, each placed in
thirty minims of a solution of one part to 43,750 of water (1 gr. to
100 oz.); so that each received 1/1600 of a grain, or .04058 mg. Of
these leaves, eleven had nearly all or a great number of their
tentacles inflected in 1 hr., and the twelfth leaf in 3 hrs. One of the
eleven had every single tentacle closely inflected in 50 m. Two leaves
out of the sixteen were only moderately affected, yet more so than any
of those simultaneously immersed in water; and the remaining two, which
were pale leaves, were hardly at all affected. Of the sixteen
corresponding leaves in water, one had nine tentacles, another six, and
two others two tentacles inflected, in the course of 5 hrs. So that the
contrast in appearance between the two lots was extremely great.
Eighteen leaves were immersed, each in thirty minims of a solution of
one part to 87,500 of water (1 gr. to 200 oz.), so that each received
137