minute doses is not so incredible as it must at first appear.
[Sulphate of Ammonia. The few trials made with this and the following
five salts of ammonia were undertaken merely to ascertain whether they
induced inflection. Half-minims of a solution of one part of the
sulphate of ammonia to 437 of water were placed on the discs of seven
leaves, so that each received 1/960 of a grain, or .0675 mg. After 1
hr. the tentacles of five of them, as well as the blade of one, were
strongly inflected. The leaves were not afterwards observed.
Citrate of Ammonia. Half-minims of a solution of one part to 437 of
water were placed on the discs of six leaves. In 1 hr. the short outer
tentacles round the discs were a little inflected, with the glands on
the discs blackened. After 3 hrs. 25 m. one leaf had its blade
inflected, but none of the exterior tentacles. All six leaves remained
in nearly the same state during the day, the submarginal tentacles,
however, [page 167] becoming more inflected. After 23 hrs. three of the
leaves had their blades somewhat inflected; and the submarginal
tentacles of all considerably inflected, but in none were the two,
three, or four outer rows affected. I have rarely seen cases like this,
except from the action of a decoction of grass. The glands on the discs
of the above leaves, instead of being almost black, as after the first
hour, were now after 23 hrs. very pale. I next tried on four leaves
half-minims of a weaker solution, of one part to 1312 of water (1 gr.
to 3 oz.); so that each received 1/2880 of a grain (.0225 mg.). After 2
hrs. 18 m. the glands on the disc were very dark-coloured; after 24
hrs. two of the leaves were slightly affected; the other two not at
all.
Acetate of Ammonia. Half-minims of a solution of about one part to 109
of water were placed on the discs of two leaves, both of which were
acted on in 5 hrs. 30 m., and after 23 hrs. had every single tentacle
closely inflected.
Oxalate of Ammonia. Half-minims of a solution of one part to 218 of
water were placed on two leaves, which, after 7 hrs., became
moderately, and after 23 hrs. strongly, inflected. Two other leaves
were tried with a weaker solution of one part to 437 of water; one was
strongly inflected in 7 hrs.; the other not until 30 hrs. had elapsed.
149