Castoreum is a substance contained in two pear-shaped pouches situated near the organs of reproduction, of a bitter taste and slightly foetid odour, at one time largely employed as a medicine, but now used only in perfumery.
In many cases the slimy masses of spermatia (Uredineae), conidia (Claviceps), basidiospores (Phallus, Coprinus), &c., emit more or less powerful odours, which attract flies or other insects, and it has been shown that bees carry the flagrant oidia of Sclerotinia to the stigma of Vaccinium and infect it, and that flies carry away the foetid spores of Phallus, just as pollen is dispersed by such insects.
The insects visit the plant in large numbers, attracted by the foetid smell, and act as carriers of the pollen from one spathe to another.