Source : Webster's Revised Unabridged Dictionary (1913)

Microsporangium \Mi`cro*spo*ran"gi*um\, n. [NL. See {Micro-},
   and {Sporangium}.] (Bot.)
   A sporangium or conceptacle containing only very minute
   spores. Cf. {Macrosporangium}.

Source : WordNet®

microsporangium
     n : a plant structure that produces microspores
     [also: {microsporangia} (pl)]