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Gamophyceae: Zygnematales: Desmidiaceae

 Cosmarium impressulum
Elfving var. impressulum

Cosmarium impressulum 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 (Illustrations of The Japanese Fresh-water Algae, 1977).
Species: Cell body small, (21-29.5)-36 μm long, (15.4-18)-26 μm wide, isthmus 5-(5.6-7)-9 μm wide, L/W=1.5; both sides of semicells with four wavy margins, all waves equal in size, side view elongated ellipsoid; cell wall smooth (Illustrations of The Japanese Fresh-water Algae, 1977).

Cosmarium impressulum Elfving var. impressulum (Section Microcosmarium), cell body 22 μm long, 19 μm wide, L/W=1.2, isthmus 6 μm wide, x 640, a small pond at Obihiro University of Agriculture and Veterinary Medicine, Obihiro city, Hokkaido, Japan, October 13, 2005 by Y. Tsukii
scale 31 μm scale 63 μm scale 94 μm; x 640
Cosmarium

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