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Gamophyceae: Zygnematales: Desmidiaceae

Cosmarium orthostichum
Lundell

Genus: Unicellular; variable in shape; a constriction at the center of the cell body; mostly longer than wide; flattened; each semicell hemispherical, spherical, ellipsoidal, rectangular, pyramidal or kidney-shaped; no apical indentation
Subgenus [Eucosmarium]: Cell body dorso-ventrally compressed, with strong constriction at the center, transverse section elliptical or diamond-shaped.
Section [Margaritiferae]: Cell surface granulated, gnarled or spiny; semicells pyramidal with flattened apex or trapezoid (Illustrations of The Japanese Fresh-water Algae, 1977).

Species:
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Cosmarium
C. orthostichum
v. subpolonica
31 x 28 μm
Uruguay, 1999
Similar species -- >> C. punctulatum; C. sphalerostichum; C. polonicum; C. horomuiensis;

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Cosmarium orthostichum
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