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the small, tightly packed apical leaves that surround an inflorescence. In plants of the families Compositae and Dipsacaceae, the involucre closely surrounds the inflorescence; as a result, the involucre and the inflorescence appear to form a single flower. In plants of the family Umbelliferae, the involucre is located at the base of the inflorescences, or compound umbels. The leaves at the base of a simple umbel form an involucel. The morphological characteristics of involucres and involucels are used in the taxonomy of the various families.