The orchis, scabius and valisneria.

The corolla of this flower (Aristolochia Clematitis), which is tubular, but terminating upwards in a ligulate limb, is inflated into a globular figure at the base. The tubular part is internally beset with stiff hairs, pointing downwards. The globular part contains the pistil, which consists merely of a germen and stigma, together with the surrounding stamens. But the stamens, being shorter than the germen, cannot discharge the pollen so as to throw it upon the stigma, as the flower stands always upright till after impregnation. And hence, without some additional and peculiar aid, the pollen must necessarily fan down to the bottom of the flower. Now, the aid that nature has furnished in this case, is that of the Tiputa Pennicornis, a small insect, which entering the tube of the corrolla in quest of honey, descends to the bottom, and rummages about till it becomes quite covered with pollen; but not being able to force its way out again, owing to the downward position of the hairs, which converge to a point like the wires of a mouse-trap, and being somewhat impatient of its confinement it brushes backwards and forwards, trying every corner, till, after repeatedly traversing the stigma, it covers it with pollen sufficient for its impregnation, in consequence of which the flower soon begins to droop, and the hairs to shrink to the sides of the tube, effecting an easy passage for the escape of the insect." — Rev. P. Keith — System of Physiological Botany.