1) Megasporangium 
• (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.
Mac`ro·spo·ran'gi·um noun [ New Latin See Macro- , and Sporangium .] (Botany) A sporangium or conceptacle containing only large spores; -- opposed to microsporangium . Both are found in the genera Selaginella , Isoctes , and Marsilia , plants...