upon, in the same way and to the same degree, by the gastric fluid of Drosera, as they are by animal pepsin. Cartilage, bone, even the enamel from teeth, were experimented upon, and it was found were dissolved by it, as well as certain vegetable substances, such as the stored-up matter of living seed, pollen grains, and the fragments of seedlings. Various experiments were made by Mr. Darwin to ascertain the effects produced by different salts. He found that o1ʊʊʊʊ of a grain of phosphate of ammonia caused a marginal tentacle to sweep through an arc of 180°. The sensitiveness, in this case, is greater than that found in the most sensitive organs of the human body. Many curious facts came to light under this close investigation. Camphor, it was found, is a violent stimulant; the poison of the cobra occasioned only slight protoplasmic changes, while liquid alcohol produced no effect whatever. In small doses the fumes of camphor, alcohol, and chloroform, threw the plant into a stupor. Carbonic acid is also a narcotic, which fact offers a curious. confirmation of the lately determined point that plants exhale, as the result of true respiration, the same gas as is given out by the breathing of animals.

The sensitiveness of the Drosera leaf appears to

be wholly confined to the glands. Unless the gland which is excited be upon a marginal tentacle, the object, or touch, that induces its own inflection also causes a radial influence to be sent outward from its base as a centre that affects, first, the nearest tentacles, and in succession, those which are farther and farther off. This impulse does not follow the fibrovascular bundles, whose arrangements may be seen in Figure 76, f; but its course seems to be determined by the form and position of the parenchymal cells of the base of the tentacles themselves and the surrounding tissue. The cells are elongated in the pedicels of the glands; they are arranged radially about the bases of the tentacles, and are longer in the longitudinal direction of the leaf. Aggregation may be seen to be obstructed by every cross division of the cell wall; the motor impulse is probably hindered in the same way, for it always travels most quickly in the direction where there is the least obstruction in the form of cell walls.

When the bending portion of a pedicel receives the impulse from its own gland, it always becomes inflected toward the centre of the leaf, and so all the glands, if immersed in any exciting fluid, turn toward the centre. When, however, the exciting substance

is placed on any other portion of the leaf, the motor impulse is so transmitted radially from the point touched that all the glands turn toward it as a centre. The motor impulse, as it ascends the pedicels of adjacent tentacles, immediately acts upon the bending portion, without first ascending to the glands, and then being transmitted downward. Some other impulse is, however, transmitted to the glands, for they begin secreting an acid substance, and the glands send back toward the bases of the pedicel that subtle force which induces aggregation. This is the only case of any thing analogous to the reflex action. of the nerve-centres of animals known in the vegetable world.

The mechanism of the movements is not well understood; while the tentacle is bent—and it has been made to curve around a complete circumference-no folds or wrinkles can be seen in the concave portion of the bending part. It is known that when inflection takes place, a portion of the fluids belonging to the cells in the concave side goes over to the convex. It is supposed that the molecules of the cell walls on the concave side of the pedicel undergo a process not unlike that of the aggregation of the cell contents.

The many experiments made upon the Drosera lead to the conclusion that its tiny rootlets perform for it only the office of imbibing moisture, while its food is in part supplied by the atmosphere, and in part by the animal matter it truly digests.

FIG. 79. LOBE OF DIONEA. [FROM NATURE.]

There are a number of other varieties of the Droseraceae. One, the Drosera binata, is an Australian plant, and has leaves which, with their footstalks, measure twenty-seven inches in length. True to its Australian traditions, it differs greatly from its foreign cousins. There are perfectly developed tentacles on the back of the leaf, which are capable of secretion, absorption, and aggregation, but not of inflection. On both surfaces of this variety are welldeveloped sessile (seated) glands, which secrete only after the absorption of some nitrogenous substance. This variety forms the connecting link between Drosera and Drosophyllum, possessing the organs of both.