The New Student's Reference Work/Involucre
In′volu′cre (in plants). A set of bracts occurring in a rosette (“whorl,” “cycle”). Bracts are leaves more or less modified, which occur in an inflorescence. In some forms of inflorescence, as in the umbel and head, the numerous pedicels arise from approximately the same point, and as each pedicel is subtended by a bract, the numerous bracts are thrown together in a rosette-like cluster which is called the involucre. A distinct involucre is present, therefore, in the head-like clusters of the composite family, in which case it resembles the calyx of an ordinary flower, and also in the umbels of the great family of umbelliferae, to which the carrots, parsnips etc. belong.