• WordNet 3.6
    • n involucre a highly conspicuous bract or bract pair or ring of bracts at the base of an inflorescence
    • ***
Webster's Revised Unabridged Dictionary
    • n Involucre (Bot) A whorl or set of bracts around a flower, umbel, or head.
    • ***
Century Dictionary and Cyclopedia
    • n involucre 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.)
    • n involucre In anatomy, a membranous envelop. as the pericardium.
    • n involucre In zoology, an involucrum.
    • ***
Chambers's Twentieth Century Dictionary
    • n Involucre in-vol-ū′kėr (bot.) a group of bracts in the form of a whorl around an expanded flower or umbel—also Involū′crum
    • ***


Webster's Revised Unabridged Dictionary
L. involucrum, a covering, wrapper, fr. involvere, to wrap up, envelop: cf. F. involucre,. See Involve
Chambers's Twentieth Century Dictionary
L. involucruminvolvĕre, to involve.


In literature:

Nuttall's flowering dogwood makes a brave display with its wealth of show involucres in the spring along cool streams.
"Steep Trails" by John Muir
An involucre of narrow, pinnately cut bracts.
"Wild Flowers Worth Knowing" by Neltje Blanchan
The involucre-scales are sometimes delicately rose-coloured.
"Explorations in Australia, The Journals of John McDouall Stuart" by John McDouall Stuart
In these the involucre is little altered, and the receptacle is attacked by larva.
"Journals of Travels in Assam, Burma, Bhootan, Afghanistan and TheNeighbouring Countries" by William Griffith
I found the first point of similarity with the filbert is in the involucre covering the nut.
"Growing Nuts in the North" by Carl Weschcke
The leaves are ternate, segments numerous; each leaf springs from the tuber, with the exception of those of the involucre.
"Hardy Perennials and Old Fashioned Flowers" by John Wood
On one of my black walnut trees there is a serious pest, a very little worm which infests the involucre.
"Northern Nut Growers Association Report of the Proceedings at the" by Various
The nuts, with their leaflike involucres, are attractive in appearance in August and September.
"Northern Nut Growers Association Report of the Proceedings at the" by Various
They are further protected by the growth of the hinder margin of the depression to form a scale-like involucre (in).
"Encyclopaedia Britannica, 11th Edition, Volume 4, Part 3" by Various
In some localities involucre borers make tunnels between the nut and the involucre, interfering with the development of the kernel.
"Northern Nut Growers Association Report of the Proceedings at the Second Annual Meeting" by Northern Nut Growers Association