The Collaborative International Dictionary of English v.0.48:

Rhaphe \Rha"phe\, n. [NL., fr. Gr. ??? seam, fr. ??? to sew. ]
   (Bot.)
   The continuation of the seed stalk along the side of an
   anatropous ovule or seed, forming a ridge or seam. [Written
   also raphe.] --Gray.
   [1913 Webster]

WordNet (r) 3.0 (2006):

rhaphe
    n 1: a ridge that forms a seam between two parts [syn: raphe,
         rhaphe]