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Antheridia consist of a thin cellular layer that holds many sperm inside. Here, the diagram of a liverwort antheridium is shown. An antheridium is a haploid structure or organ producing and containing male gametes (called antherozoids or sperm). The plural form is antheridia, and a structure containing one or more antheridia is called an ...
Antheridia and archegonia occur on different gametophytes, which are then called dioicous. The moss Mnium hornum has the gametophyte as the dominant generation. It is dioicous: male plants produce only antheridia in terminal rosettes, female plants produce only archegonia in the form of stalked capsules. [26] Seed plant gametophytes are also ...
The thallus (tissue) consists of fine branched filaments each with a central axial filament supporting pericentral cells. [7] The number of these pericentral cells (4–24) is used in identification. [8] [9] [10] Polysiphonia elongata [11] shows a central axial cell with 4 periaxial cells with cortical cells growing over the outside on the ...
The green, photosynthetic part of the plant is technically a megaphyll and in ferns, it is often called a frond. New leaves typically expand by the unrolling of a tight spiral called a crozier or fiddlehead into fronds. [9] This uncurling of the leaf is termed circinate vernation. Leaves are divided into two types: sporophylls and tropophylls.
The biflagellate sperm must swim from the antheridia, or else be splashed to the archegonia. When this happens, the sperm and egg cell fuse to form a zygote, the cell from which the sporophyte stage of the life cycle will develop. Unlike all other bryophytes, the first cell division of the zygote is longitudinal. Further divisions produce three ...
Spores that are buried underground, if reached by antheridiogen, can form gametophytes that reach the surface. Or, they form a small amount of antheridia, and the sperm produced can reach the female gametophytes above ground. The way in which the sex of each individual is determined is a form of environmental sex determination (ESD).
Some antheridia do not release their sperm. For example, the oomycete antheridium is a syncytium with many sperm nuclei and fertilization occurs via fertilization tubes growing from the antheridium and making contact with the egg cells. Antheridia are common in the gametophytes in "lower" plants such as bryophytes, ferns, cycads and ginkgo.
The antheridia (or globules [6]) and oogonia (or nucules [6]) are protected by a layer of sterile cells when mature; the oogonium is oblong in shape and consists of a single egg, while the spherical antheridium is packed with threadlike cells that produce spermatia. As a result, the Characeae have the most complex structure of all green algae.