Cosmarium Corda ex Ralfs

One of the most species rich desmid genera with >1200 species. It lacks distinctive features similar to those defining other genera and it is often based on negative characters. Some basic characters: end view often compressed, absence of spines, apex of cell neither cleft nor indented, cells solitary. (Croasdale, H. & Flint, E. 1988. Flora of New Zealand Desmids II. - Caxton Press, Christchurch.)

Cosmarium blyttii Wille
Dimensions: L. (10)13–20 µm, B. (9)12– 18 µm. Coesel 1991.

Cosmarium contractum Kirchn.
Dimensions: L. 30–50 µm, B. 20–30 µm. Lenzenweger 1999. Krieger & Gerloff 1962.

Cosmarium depressum (Näg.) Lund. f. minutum Heimerl.
Dimensions: L. 14–18 µm, B. 18–21 µm. Lenzenweger 1999.
Gelatinous rods secreted through the cell wall are visible on the picture.

Cosmarium sp. cf. kirchneri Börges. C. margaritiferum v. kirchneri)
Dimensions: L. 50–75 µm, B. 44–60 µm. Coesel 1991, Lenzenweger 1999.

Cosmarium subcucumis Schmidle
Dimensions: L. 40–80 µm, B. 30–50 µm. Coesel 1991, Lenzenweger 1999.