Macrosporangium :: Macrosporangium (n.) A sporangium or conceptacle containing only large spores; -- opposed to microsporangium. Both are found in the genera Selaginella, Isoctes, and Marsilia, plants remotely allied to ferns..
Microsporangium :: Microsporangium (n.) A sporangium or conceptacle containing only very minute spores. Cf. Macrosporangium.