Cuar. XVI.] MOVEMENTS OF THE LEAVES. 303 
fora longer time. The margins, with the drops, became plainly 
incurved in 2 hrs. 17 m. The incurvation subsequently increased 
somewhat, but after 24 hrs. had greatly decreased. 
Experiment 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 experi- 
ment we learn that the motor impulse can be transmitted to a dis- 
tance 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 hr. 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 [this 
and] the following case, that this holds good with Pinguicula. 
Experiment 15.—A row of drops of a solution of one part of 
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. 80m. 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 strength acts powerfully on Drosera, 
and it is just possible that the solution was too strong. I regret that 
I did not try a weaker solution. 
Experiment 17.—As the pressure from bits of glass causes incurvation, 
I scratched the margins of two leaves for some minutes with a blunt 
needle, but no effect was produced. The surface of a leaf beneath a 
drop of a strong infusion of raw meat was also rubbed for 10 m. with 
the end of a bristle, so as to imitate the struggles of a captured insect ; 
but this part of the margin did not bend sooner than the other parts 
with undisturbed drops of the infusion. 
We learn from the foregoing experiments that the margins 
of the leaves curl inwards when excited by the mere pressure 
