Species [ var. tenuis Agardh ]: Trichome straight, bluegreen, slightly curved at terminal, 2.5-5 μm long, 4-10 μm wide, L/W=1/3 (0.3); septum slightly constricted, granules present along septum; apical cells semispherical, its wall sometimes thickened. [ var. asiatica Wille ]: 4.5-6 μm long, 10-12 μm wide (Illustrations of The Japanese Fresh-water Algae, 1977).

31 μm 63 μm 94 μm; x 640

Images of collecting locality: a small marsh pond near memorial pole of Saito Mokichi (close to Iroha-numa), Zao mountain, Yamagata city, Yamagata Pref., Japan, August 2, 2006 by Y. Tsukii