Experiment 11.—­Fragments of glass were placed on the margins of two fine young leaves.  After 2 hrs. 30 m. the margin of one certainly became slightly incurved; but the inflection never increased, and disappeared in 16 hrs. 30 m. from the time when the fragments were first applied.  With the second leaf there was a trace of incurvation in 2 hrs. 15 m., which became decided in 4 hrs. 30 m., and still more strongly pronounced in 7 hrs., but after 19 hrs. 30 m. had plainly decreased.  The fragments excited at most a slight and doubtful increase of the secretion; and in two other trials, no increase could be perceived.  Bits of coal-cinders, placed on a leaf, produced no effect, either owing to their lightness or to the leaf being torpid.

Experiment 12.—­We now turn to fluids.  A row of drops of a strong infusion of raw meat were placed along the margins of two leaves; squares of sponge soaked in the same infusion being placed on the opposite margins.  My object was to ascer- [page 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 incurvation; 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 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 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.