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A sporangium bearing microspores.



the multicellular organ of heterosporous Pteridophyta and seed plants in which the microspores develop. In Selaginella and Sigillaria the microsporangia are located singly in the axils of microsporophylls or on the upper-sides of the leaves (in Lepidodendron, Pleuromeia, and Isoetes). In Pleuromeia and Isoetes they are submerged in a special cavity. In some extinct ferns the microsporangia are on the underside of the sporophylls. In water ferns they are formed in sporocarps: 64 microspores develop in the microsporangium of Sahinia, and 32 or 64 in the microsporangium of Marsilea. In gymnosperms the microsporangia develop singly on microsporophylls (in some joint firs); more often several develop on a microsporophyll, arranged singly (conifers), in sori (many sago palms, ginkgoes) or in synangia (Caytoniales, many Bennettitales, Ephedra, Welwitschia). In angiosperms the pollen sac of the anther is homologous to the microsporangium.

References in periodicals archive ?
The latter may be particularly important for grains in newly opened anthers and microsporangia.
Because of boundary-layer effects, mean wind speeds corresponding to u[prime] for a particular pollen type are typically insufficient to liberate pollen grains from anthers, microsporangia, or vegetative surfaces.
Individual anthers and microsporangia certainly have reduced boundary layers compared to leaf Surfaces.
strobus) in Arizona, New York, and Wyoming indicate that little pollen is shed from dehisced microsporangia without agitation, and that newly dehisced microstrobili are emptied of virtually all pollen after a single dry, sunny day with energetic wind gusts (S.
The compound pollen strobili of Austrotaxus have a unique arrangement whereby the stalks of the microsporophylls are vestigial, the microsporangia of each microsporophyll are fused to each other and partially adnate to the microsporophyll itself (Saxton, 1934; Wilde, 1975).
10; microsporophylls 6-14, perisporangiate, radially symmetrical, peltate, each bearing 4-9 microsporangia.
The microsporangia of Taxus, as with Pseudotaxus, are distinctive among conifers in that they are radial (as opposed to being positioned only abaxially on the sporangiophore), which has led Wilde (1975) to suggest that the pollen strobilus is a reduced lateral one.
Pollen strobili simple, axillary, on the most recent year's branchlets, borne on minute recurved peduncles so that the strobili are most easily visible from the lower surface of the branchlet, 4-10 mm long, subtended by 12 or 16 keeled sterile scales arranged in 4 vertical rows; microsporophylls numerous (20-36), arranged in alternating whorls of 4, hyposporangiate (occasionally perisporangiate), dorsiventral, each with (3-)4(-6-7) microsporangia.