Ouar. XVI. MOVEMENTS OF THE LEAVES. 375 
tain whether a fluid would act as energetically as a substance 
yielding the same soluble matter to the glands. No distinct 
difference was perceptible; certainly none in the degree of in- 
curvation ; but the incurvation round the bits of sponge lasted 
rather longer, as might perhaps have been expected from the 
sponge remaining damp and supplying nitrogenous matter for a 
longer time. The margins, with the drops, became plainly 
incurved in 2hrs.17m. Theincurvation subsequently increased 
somewhat, but after 24 hrs. had greatly decreased. 
Euperiment 13.—Drops of the same strong infusion of raw 
meat were placed along the midrib of a young and rather deeply 
concave leaf. The distance across the broadest part of the leaf, 
between the naturally incurved edges, was ‘55 of an inch (13-97 
mm.). In 3 hrs. 27 m. this distance was a trace less; in 6 hrs. 
27 m. it was exactly -45 of an inch (11:43 mm.), and had therefore 
decreased by °1 of an inch (2°54 mm.). After only 10 hrs. 37 m. 
the margin began to re-expand, for the distance from edge to 
edge was now a trace wider, and after 24 hrs. 20 m. was as 
“great, within a hair’s breadth, as when the drops were first 
placed on the leaf. From this experiment we learn that the 
motor impulse can be transmitted to a distance of ‘22 of an 
inch (5°590 mm.) in a transverse direction from the midrib to 
both margins; but it would be safer to say ‘2 of an inch 
(5°08 mm.), as the drops spread a little beyond the midrib, 
The incurvation thus caused lasted for an unusually short time. 
Experiment 14.—Three drops of a solution of one part of 
carbonate of ammonia to 218 of water (2 grs. to 1 oz.) were 
placed on the margin of a leaf. These excited so much secretion 
that in 1 h. 22 m. all three drops ran together; but although the 
leaf was observed for 24 hrs., there was no trace of inflection. 
We know that a rather strong solution of this salt, though it 
does not injure the leaves of Drosera, paralyses their power of 
movement, and I have no doubt, from the following case, that 
this holds good with Pinguicula. 
Experiment 15—A row of drops of a solution of one part ot 
carbonate of ammonia to 875 of water (1 gr. to 2 oz.) was placed 
on the margin of a leaf. In 1 hr. there was apparently some 
slight incurvation, and this was well marked in 3 hrs. 30 m. 
After 24 hrs. the margin was almost completely re-expanded. 
Experiment 16.—A row of large drops of a solution of one 
part of phosphate of ammonia to 4375 of water (1 gr. to 10 oz.) 
was placed along the margin of a leaf. No effect was produced, 
and after 8 hrs. fresh drops were added along the same margin 
without the least effect. We know that a solution of this 
25 
