Genus: Colonies of fixed number of cells, flat, circular in shape; cell body polygonal in shape,
with horn-like projections; cell wall garanulated, wrinkled or notched;
chloroplasts plate-like or reticular; asexual reproduction by zoospore; sexual reproduction by isogametes
(Illustrations of The Japanese Fresh-water Algae, 1977).
Pediastrum tetras, colonies of 8 cells, x 400, x 640, Uruguay 1999, photo by Y. Tsukii