involucre

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A series of bracts beneath or around a flower or flower cluster.

Century Dictionary and Cyclopedia

1. n. In botany, any collection of bracts round a cluster of flowers. In umbelliferous plants it consists of separate narrow bracts placed in a single whorl; in many composite plants these organs are imbricated in several rows. In some species of Cornus, many Labiatæ, and other plants, the involucre is white or variously colored, constituting the showy part of the flower. (See cut.) The same name is given also to the superincumbent covering or indusium of the sori of ferns. (See indusium, 2.) In some species of Equisetum the involucre is the annulus or annular girdle situated between the uppermost whorl of leaf-sheaths and the whorl of sporangiferous scales. (Bennett and Murray, Crypt. Bot‥ p. 110.)
2. n. In anatomy, a membranous envelop. as the pericardium.
3. n. 3, In zoology, an involucrum.

Wiktionary

1. n. Conspicuous bract, bract pair or ring of bracts at the base of an inflorescence.

GNU Webster's 1913

1. n. A whorl or set of bracts around a flower, umbel, or head.
2. n. A continuous marginal covering of sporangia, in certain ferns, as in the common brake, or the cup-shaped processes of the filmy ferns.
3. n. The peridium or volva of certain fungi. Called also involucrum.

WordNet 3.0

1. n. a highly conspicuous bract or bract pair or ring of bracts at the base of an inflorescence