heterospory

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Related to heterosporous: homosporous

heterospory

the formation of more than one sort of SPORE, usually MICROSPORES and MEGASPORES in ferns and seed plants, giving rise to distinct male and female GAMETOPHYTE generations. The terms mega-and microspore were first used in connection with PTERIDOPHYTES where differences in spore size occur. Later, because of how the structures are formed, these terms were used in reference to seed plants where such size differences are rarer. Here the microspore is the pollen, and the megaspore is the cell which gives rise to the EMBRYO SAC.
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Plants arising from the ground in tufts; stems a corm; leaves quill-like, 1-3 dm long and 1-3 mm wide; heterosporous with sporangia on the adaxial leaf bases.
Stems creeping close to the ground to erect, sometimes forming large dense mats, often occurring as individual stems on clay banks; leaves in 4 row, margins finely toothed; heterosporous with terminal strobili 1-2 cm long, 4-angled.
Isoetes is heterosporous, with each leaf a potential microsporophyll or megasporophyll.
The remaining living ferns consist of heterosporous leptosporangiate genera that are either amphibious (Marsileales) or floating aquatics (Salviniales; Gifford & Foster, 1989).
Comparative leaf structure of six species of heterosporous ferns.