noun. A sporangium containing macrospores. It is homologous with the ovule of flowering plants. Also called goniotheca.

noun. 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.

noun. A sporangium or conceptacle containing only large spores; opposed to microsporangium. Both are found in the genera Selaginella, Isoetes, and Marsilea, all of which are ferns or remotely allied to ferns.

noun. a plant structure that produces megaspores

"Consult one of the best of them, Webster's New World Dictionary, and what you find is a miniature encyclopedia filled with the explanations of initials, proper names, and entries like "macrosporangium" and "abhenry," which are not and never will be words of the English language."

microsporangium  

sporangium  spore case  spore sac  

macrosporangia