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ASSISTANCE OF INSECTS IN IMPREGNATION.
Professor Willdenow concerning the Aristolochia Clematitis, Engl. Bot. t. 398. The stamens and pistils of this flower are enclosed in its globular base, the anthers being under the stigma, and by no means commodiously situated for conveying their pollen to it. This therefore is accomplished by an insect, the Tipula pennicornis, which enters the flower by the tubular part. But that part being thickly lined with inflexed hairs, though the fly enters easily, its return is totally impeded, till the corolla fades, when the hairs lie flat against the sides, and allow the captive to escape. In the mean while the insect, continually struggling for liberty, and pacing his prison round and round, has brushed the pollen about the stigma. I do not doubt the accuracy of this account, though I have never caught the imprisoned Tipula. Indeed I have never seen any fruit formed by this plant. Probably for want of some insect adapted to the same purpose in its own country, the American Aristolochia Sipho, though it flowers plentifully, never forms fruit in our gardens.