Genus:
Variable in shape; strong constriction at center; semicell ellipsoidal, polygonal, etc.;
cell wall with simple or branching spines, most of them laterally aligned;
4 plate-like chloroplasts in each semicell; one or more pyrenoids in each chloroplast
(Illustrations of The Japanese Fresh-water Algae, 1977).
Species:
Xanthidium armatum (Brébisson) Rabenhorst ex Ralfs ,
cell body 113 μm long, 80 μm wide (excluding spines), L/W=1.4, isthmus 35 μm wide,
spiny projections about 8 μm long,
x 640, Shimo-no-koike (pond), Shiga highland, Yamanouchi town, Nagano Pref., Japan, June 19, 2005 by Y. Tsukii
50 μm
100 μm
150 μm; x 400 :
31 μm
63 μm
94 μm; x 640
Xanthidium armatum (Brébisson) Rabenhorst ex Ralfs:
Cell body (without spines) 115-153 μm long, 81-104 μm wide,
isthmus 35-42 μm wide (Illustrations of the Fresh-water Algae, 1977).