Phylum Chlorophyta; sub-phylum Chlorophyceae; Order Zygnematales
There are two groups of Desmids: the "Placoderm" and the "Saccoderm" Desmids.
Placoderm desmids have cells composed of two halves (semicells), often almost divided from each other by deep median incisions. The cells are symmetrical about 3 planes, and often bear elaborate ornamentation. Genera are Cosmarium, Cosmocladium, Euastrum, Micrasterias, Staurastrum, Staurodesmus, Xanthidium.
Saccoderm desmids are simple shapes, cylindrical or spindle-shaped, rarely with any median constriction. This group forms the family Mesotaeniaceae and includes the genera Cylindrocystis, Mesotaenium, Netrium, Roya, Spirotaenia, Tortitaenia, and, in the suborder Closteriinae, Closterium, Gonatozygon and Penium, and in the suborder Desmidiinae, Actinotaenium.
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|Cell composed of 2 symmetrical semicells with relatively flat aspect in face view (apical view elliptical). Cells generally have an apical notch and are more deeply incised around the margin.|
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