\In"vo*lu`cre\ (?; 277), n. [L. involucrum a covering,
wrapper, fr. involvere to wrap up, envelop: cf. F. involucre.
See {Involve}.] (Bot.)
(a) A whorl or set of bracts around a flower, umbel, or head.
(b) A continuous marginal covering of sporangia, in certain
    ferns, as in the common brake, or the cup-shaped
    processes of the filmy ferns.
(c) The peridium or volva of certain fungi. Called also
    {involucrum}.