Camphor.—Some scraped camphor was left for a day in a bottle with distilled water, and then filtered. A solution thus made is said to contain 1/1000 of its weight of camphor; it smelt and tasted of this substance. Ten leaves were immersed in this solution; after 15 m. five of them were well inflected, two showing a first trace of movement in 11 m. and 12 m.; the sixth leaf did not begin to move until 15 m. had elapsed, but was fairly well inflected in 17 m. and quite closed in 24 m.; the seventh began to move in 17 m., and was completely shut in 26 m. The eighth, ninth, and tenth leaves were old and of a very dark red colour, and these were not inflected after an immersion of 24 hrs.; so that in making experiments with camphor it is necessary to avoid such leaves. Some of these leaves, on being left in the solution for 4 hrs., became of a rather dingy pink colour, and secreted much mucus; although their tentacles were closely inflected, the protoplasm within the cells was not at all aggregated. On another occasion, however, after a longer immersion of 24 hrs., there was well marked aggregation. A solution made by adding two drops of camphorated spirits to an ounce of water did not act on one leaf; whereas thirty minims added to an ounce of water acted on two leaves immersed together. M. Vogel has shown* that the flowers of various plants do not wither so soon when their stems are placed in a solution of camphor as when in water; and that if already slightly withered, they recover more quickly. The germination of certain seeds is also accelerated by the solution. So that camphor acts as a stimulant, and it is the only known stimulant for plants. I * ‘Gardener’s Chronicle,’ 1874, p. 671. Nearly similar observations were made in 1798 by B. S. Barton. [page 210] wished, therefore, to ascertain whether camphor would render the leaves of Drosera more sensitive to mechanical irritation than they naturally are. Six leaves were left in distilled water for 5 m. or 6 m., and then gently brushed twice or thrice, whilst still under water, with a soft camel-hair brush; but no movement ensued. Nine leaves, which had been immersed in the above solution of camphor for the times stated in the following table, were next brushed only once with the same brush and in the same manner as before; the results are given in the table. My first trials were made by brushing the leaves whilst still immersed in the solution; but it occurred to me that the viscid secretion round the glands would thus be removed, and the camphor might act more effectually on them. In all the following trials, therefore, each leaf was taken out of the solution, waved for about 15 s. in water, then placed in fresh water and brushed, so that the brushing would not allow the freer access of the camphor; but this treatment made no difference in the results.