Species [var. digitus]: Cell body 130-300 μm long, 40-84 μm wide, L/W = 3-4; cell wall smooth. [var. lamellosum]: Longer than v. digitus, both sides parallel; cell body 140-416 μm long, 32-60 μm wide, L/W = 5-8. [var. naegelii]: Smaller than v. digitus, both ends broadly rounded; cell body 100-200 μm long, 25-36 μm wide, L/W = 4-5. [var. rectum]: Larger than v. digitus, tapered to both ends; cell body 300 μm long, 48 μm wide, L/W = 6.3 (Illustrations of The Japanese Fresh-water Algae, 1977).

50 μm 100 μm 150 μm; x 400 : 31 μm 63 μm 94 μm; x 640

Netrium digitus var. lamellosum ?, stock Tnc, a dividing cell, axenic cluture, x 400, x 640, Chyausu-Dake (mountain), Nasu town, Tochigi Pref., October 2000, collected by H. Shiomizu, photo by Y. Tsukii

Netrium digitus (Ehrenberg) Itzingsohn et Rothe var. digitus: Vegetative cells spindle-shaped, L/W = 3-4, 130-300 μm long, 40-84 μm diam. chloroplasts consist of central axis and 6 radial ridges (Illustrations of The Japanese Fresh-water Algae, 1977).

Netrium digitus var. naegelii (Brébisson) Krieger: Vegetative cells spindle-shaped, L/W = 4-5 100- (124-190) -200 μm long, 25- (28-36) μm diam. (Illustrations of The Japanese Fresh-water Algae, 1977).

Netrium digitus var. lamellosum (Brébisson) Grünblad: Vegetative cells spindle-shaped, L/W = 5-8, 140- (272-416) μm long, 32- (42-59) -60 μm diam. chloroplasts consist of central axis and 6 radial ridges (Illustrations of The Japanese Fresh-water Algae, 1977).