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Show 374 PINGUICULA VULGARIS. CnAr. XVI. Experiment 9.-A chain of fibres of roast meat, as thin as bristles and moistened with saliva, were placed down one whole side, close to the narrow, naturally incurved. edge of a leaf. In 3 hrs. this side was greatly incurved along Its whole length, and after 8 hrs. formed a cylinder, about •lo of an inch (1·27 mm.) in diameter, quite concealing the meat. rrhis cylinder remained closed for 32 hrs., but after 4B hrs. was half unfolded, and in 72 hrs. was as open as the opposite margin where no meat had been placed. As the thin fibres of meat w~re completely overlapped by the margin, they wore not pushed at all inwards, across the blade. Experiment 10.-Six cabbage seeds, soaked . for a night in water were placed in a row close to the narrow Incurved edge of a leaf. We shall hereafter see that these seeds yield soluble matter to the glands. In 2 hrs. 25m. the margin was decidedly inflected; in 4 h.rs. it extended over the seeds for about half their breadth, and in 7 hrs. over three-fourths of their breadth, forming a cylinder not quite closed along the inner .side, and about · 7 of an inch (1·77B mm.) in diameter. After 24 hrs. the inflection had not increased, perhaps had decreased. The glands which had been brought into contact with the upper surfaces of the seeds were now secreting freely. In 36 hrs. from the time when the seeds were put on the leaf the margin bad greatly, and after 48 hrs. had completely, ro-expanded. As the seeds were no longer held by the inflected margin, and as the secretion was beginning to fail, they rolled some way down the marginal channel. 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. vVith tho 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 sUght and Joubtful 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. Expuiment 12.-We will 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- CuAr. XVI. MOVEMENTS OF TilE LEA YES. 375 tain whether a fluid vvoulJ act as enoro·etically as a substance yielding the same soluble matter to th~ glands. No distinct difference was perceptible; certainly none in the degree of incurvation; but the incurvation round the bits of spono-e 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 incurvod in 2 hrs. 17m. 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 mrn.). In 3 hrs. 27 m. this distance was a trace loss; in 6 lll's. 27m. 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 11l's. 37m. 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 tho 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 (5·588 mm.) in a transverse direction from the midrib to both margin!:i; 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. .ft'xp~rimerd 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. 22m. all throe drops ran together; but although tho leaf was observed for 24 hrs., there was no trace of inflection. We know that a rather strong solution of this salt, though it docs 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 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 appanmtly same slight incurvation, and this was well marked ·in 3 hi·s. 30 m. After 24 hrs. the margin was almost completely re-expanded. Experintent 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 tho same margin )Vithout the least effect. We know that a solution of this |