Genus: Colonies of a 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 duplex or P. muticum ??,
a colony of 30 and 16 cells (30 = 14 [-2?] + 11 + 5; 16 = 11 + 5 ),
x 400, Japan, 1998 by Y. Tsukii