The Collaborative International Dictionary
Involucel
Involucel \In*vol"u*cel\ (?; 277), n. [Dim. of involucre, or involucrum: cf. F. involucelle.] (Bot.) A partial, secondary, or small involucre. See Illust. of Involucre.
Wiktionary
involucel
n. (context botany English) An involucre that forms at the base of a flower cluster within a compound inflorescence.