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.

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Taxonomy
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Defination from the web:
macrosporangium. 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. ...