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An anther and its filament together form a typical (or filantherous) stamen, part of the male floral organ. The typical anther is bilocular, i.e. it consists of two thecae. Each theca contains two microsporangia, also known as pollen sacs. The microsporangia produce the microspores, which for seed plants are known as pollen grains.
Encephalartos villosus microsporophylls with microsporangia. A microsporangium (pl. microsporangia) is a sporangium that produces microspores that give rise to male gametophytes when they germinate. Microsporangia occur in all vascular plants that have heterosporic life cycles, such as seed plants, spike mosses and the aquatic fern genus Azolla.
Conifers typically bear their microsporangia on microsporophylls aggregated into papery pollen strobili, and the ovules, are located on modified stem axes forming compound ovuliferous cone scales. Flowering plants contain microsporangia in the anthers of stamens (typically four microsporangia per anther) and megasporangia inside ovules inside ...
Diagram of stamen. A stamen typically consists of a stalk called the filament and an anther which contains microsporangia.Most commonly anthers are two-lobed (each lobe is termed a locule) and are attached to the filament either at the base or in the middle area of the anther.
In heterosporous plants, sporophylls (whether they are microphylls or megaphylls) bear either megasporangia and thus are called megasporophylls, or microsporangia and are called microsporophylls. The overlap of the prefixes and roots makes these terms a particularly confusing subset of botanical nomenclature.
The microsporangia of gymnosperms develop in pairs toward the bases of the scales, which are therefore called microsporophylls. Each of the microsporocytes in the microsporangia undergoes meiosis, producing four haploid microspores. These develop into pollen grains, each consisting of four cells and, in conifers, a pair of external air sacs.
Eusporangiate ferns are vascular spore plants, whose sporangia arise from several epidermal cells and not from a single cell as in leptosporangiate ferns.Typically these ferns have reduced root systems and sporangia that produce large amounts of spores (up to 7000 spores per sporangium in Christensenia).
Most famous parts of the brain highlighted in different colours The human brain anatomical regions are ordered following standard neuroanatomy hierarchies. Functional , connective , and developmental regions are listed in parentheses where appropriate.