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.

Cosmarium	Cosmocladium	Euastrum	Micrasterias	Staurastrum	Staurodesmus	Xanthidium
Saccoderm:	Closteriinae		Mesotaeniaceae		Desmidiinae

	MICRASTERIAS	Unicellular Desmid, forming a flat plate: semicells are divided by several deep incisions.
		Micrasterias americana
		Micrasterias crux-melitensis
		Micrasterias fimbriata
		Micrasterias jenneri
		Micrasterias papillifera
		Micrasterias pinnatifida
		Micrasterias radiosa
		Micrasterias rotata
		Micrasterias thomasiana v. notata
		Micrasterias truncata

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John Kinross