Source : Webster's Revised Unabridged Dictionary (1913)

Nemathecium \Nem`a*the"ci*um\ (? or ?), n.; pl. {Nemathecia}.
   [NL., fr. gr. ? a thread + ? a box.] (Bot.)
   A peculiar kind of fructification on certain red alg[ae],
   consisting of an external mass of filaments at length
   separating into tetraspores.