verticil

from WordNet (r) 3.0 (2006)

verticil
    n 1: a whorl of leaves growing around a stem

from The Collaborative International Dictionary of English v.0.48

Verticil \Ver"ti*cil\, n. [L. verticillus, dim. of vertex a
   whirl: cf. F. verticille. See {Vertex}.] (Bot.)
   A circle either of leaves or flowers about a stem at the same
   node; a whorl. [Written also {verticel}.]
   [1913 Webster]