It is well known that the orchids exhibit, in their mode of fertilization, remarkable adaptations by which the visits of insects are rendered subservient to the needs of the plant. In the Catasetums, for example, the male flower may be described as consisting of two parts--a lower part, the cup-like labellum (Fig. 9, _l_), which constitutes a landing-stage on which insects may alight; and an upper part, the column (Fig. 9, _c_), surrounded by the upper sepal and petals. In the upper part of the column the pollen-masses are borne at one end of an elastic pedicel, at the other end of which is an adhesive disc, and the rod is bent over a pad so as to be in a state of strain. The disc is retained in position by a membrane with which two long tubular horns (Figs. 9, _h_; 10, _an_) are continuous. These project over the labellum, where insects alight to gnaw its sweet fleshy walls, and if they be touched, even very lightly, they convey some stimulus to the membrane which surrounds and connects the disc with the adjoining surface, causing it instantly to rupture; and as soon as this happens, the disc is suddenly set free. The highly elastic pedicel then flirts the disc out of its chamber with such force that the whole is ejected, sometimes to a distance of two or three feet, bringing away with it the two pollen-masses. “The utility of so forcible an ejection is to drive the soft and viscid cushion of the disc against the hairy thorax of the large hymenopterous insects which frequent the flowers. When once attached to an insect, assuredly no force which the insect could exert would remove the disc and pedicel, but the caudicles [by which the pollen-masses are attached] are ruptured without much difficulty, and thus the balls of pollen might readily be left on the adhesive stigma of the female flower.”[10] [Illustration: FIG. 9.--Flower of _Catasetum_; _c_, column; _h_, horns; _l_, labellum.] Here again we have adaptive behaviour of exquisite nicety, and we have the transmission of an impulse very rapidly along the cells of the irritable horns, followed by the sudden rupture of a membrane. Beautiful, however, as is the adaptation, effective as it is to a definite biological end, the organic behaviour does not afford any indication of the guidance of consciousness. Among plants we have many interesting and admirable examples of organic behaviour; but nowhere so much as a hint of that profiting by individual experience which is the criterion of the effective presence of conscious guidance and control. [Illustration: FIG. 10.--_Catasetum_; C, diagram of column; _a_, anther; _an_, horn; _d_, adhesive disc; _f_, filament of anther; _g_, ovarium; _ped_, pedicel; D and E, pollinium; _p_, pollen-mass. (From Darwin’s “Orchids.”)] V.--REFLEX ACTION