304 PINGUICULA VULGARIS. (Cmr. XVI. 
of objects not yielding any soluble matter, by objects yield- 
ing such matter, and by some fluids—namely an infusion of 
raw meat and a weak solution of carbonate of ammonia. A 
stronger solution of two grains of this salt to an ounce of 
water, though exciting copious secretion, paralyses the leaf. 
Drops of water and of a solution of sugar or gum did not 
cause any movement. Scratching the surface of the leaf for 
some minutes produced no effect. Therefore, as far as we at 
present know, only two causes—namely slight continued 
pressure and the absorption of nitrogenous matter—excite 
movement. It is only the margins of the leaf which bend, 
for the apex never curves towards the base. The pedicels 
of the glandular hairs have no power of movement. I 
observed on several occasions that the surface of the leaf 
became slightly concave where bits of meat or large flies had 
long lain, but this may have been due to injury from over- 
stimulation.* 
The shortest time in which plainly marked movement was 
observed was 2 hrs. 17 m., and this occurred when either 
nitrogenous substances or fluids were placed on the leaves; 
but I believe that in some cases there was a trace of move- 
ment in 1 hr. or 1 hr. 30 m. The pressure from fragments 
of glass excites movement almost as quickly as the absorption 
of nitrogenous matter, but the degree of incurvation thus 
caused is much less. After a leaf has become well incurved 
and has again expanded, it will not soon answer to a fresh 
stimulus. The margin was affected longitudinally, upwards 
or downwards, for a distance of +13 of an inch (3:302 mm.) 
from an excited point, but for a distance of +46 of an inch 
between two excited points, and transversely for a distance 
of -2 of an inch (5°08 mm.). The motor impulse is not 
accompanied, as in the case of Drosera, by any influence 
causing increased secretion; for when a single gland was 
strongly stimulated and secreted copiously, the surrounding 
glands were not in the least affected. The incurvation of 
the margin is independent of increased secretion, for frag- 
ments of glass cause little or no secretion, and yet excite 
movement: whereas a strong solution of carbonate of am- 
monia quickly excites copious secretion, but no movement. 
* [Batalin (‘ Flora,’ 1887) believes accompanied by actual growth, and 
that the depressions are due to the thus a permanent alteration in the 
fact that the curvature of the leaf is form of the leaf is effected.—F. D.] 
