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an order or class of green algae that resemble branching or nonbranching filaments. The cells are uninucleate with parietal dissection or reticular chloroplast. The outer layer of the membrane contains chitin. The membranes of some cells have narrow zonules in the form of truncated cones; the zonules are traces of the tearing of the outer layer of the membrane during cell division. Reproduction is asexual (large zoospores equipped in front with a crown of flagella form singly in the cell) or sexual (oogamy). In some Oedogoniales the spermatozoids are formed in pairs in special disk-like cells. In others, disk-like cells produce small zoospores that germinate on or near oogoniums into dwarf male plantlets.
Oedogoniales are found widely in fresh waters, especially in warm and sluggish reservoirs. There are 470 species, making up three genera. About 100 species occur in the USSR.