The Collaborative International Dictionary of English v.0.48:

Diphyllous \Diph"yl*lous\ (d[i^]f"[i^]l*l[u^]s or
   d[-i]*f[i^]l"-), a. [Gr. di- = di`s- twice + fy`llon leaf:
   cf. F. diphylle.] (Bot.)
   Having two leaves, as a calyx, etc.
   [1913 Webster]