perigone
Per"i*gone, n. Etym: [Pref. peri- + Gr. 1. (Bot.) (a) Any organ inclosing the essential organs of a flower; a perianth. (b) In mosses, the involucral bracts of a male flower. 2. (Zoöl.) Defn: A sac which surrounds the generative bodies in the gonophore of a hydroid.