Megasporangium(redirected from megasporangia)
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in heterosporous Pteridophyta and in seed plants, the organ in which one or several megaspores develop. Megasporangia are found singly in the axils of sporophylls (in Selaginella), on the sporophyll in a special cavity (in Isoetes), or inside sporocarps (in the order Hydropteridales). In seed plants the nucellus—the central part of the ovule—is homologous to the megasporangium.