The Collaborative International Dictionary of English v.0.48:
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. [1913 Webster]WordNet (r) 3.0 (2006):
microsporangium n 1: a plant structure that produces microspores