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.

Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005

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References in periodicals archive

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.

Pteridophytes of southeast Alabama: Dichotomous keys, illustrations and distribution maps

spores of both homosporous and heterosporous Filicopsida.

Microspore morphology of Isoetes species (Lycophyta) from southern South America. Part II. tem analysis of some selected types

Isoetes is heterosporous, with each leaf a potential microsporophyll or megasporophyll.

Ornamentation of Isoetes (isoetaceae, Lycophyta) microspores

The remaining living ferns consist of heterosporous leptosporangiate genera that are either amphibious (Marsileales) or floating aquatics (Salviniales; Gifford & Foster, 1989).

FOSSILS AND FERN PHYLOGENY

Comparative leaf structure of six species of heterosporous ferns.

Occurrence of endodermis with a casparian strip in stem and leaf

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