involucre

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. [ 1913 Webster ]