Source : Webster's Revised Unabridged Dictionary (1913)

Apothecium \Apo`*the"ci*um\, n.; pl. {Apothecia}. [NL.] (Bot.)
   The ascigerous fructification of lichens, forming masses of
   various shapes.

Source : WordNet®

apothecium
     n : a cuplike ascocarp in many lichens and ascomycetous fungi
     [also: {apothecia} (pl)]