The Collaborative International Dictionary of English v.0.48:

Vaginula \Va*gin"u*la\, n. [L., dim. of vagina sheath.] (Bot.)
   (a) A little sheath, as that about the base of the pedicel of
       most mosses.
   (b) One of the tubular florets in composite flowers.
       --Henslow.
       [1913 Webster]