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).
Species: Colonies of 8-32 (rarely 4, 64 or 128 cells) with large intercellular space; inner cells H or X-shaped, trapezoid to rectangular when matured; outer half of the marginal cells prolonged into two horn-like processes with a tuft of long bristles; daughter colonies formed in a vesicle released from mother cell; cell wall smooth (Photomicrographs of the fresh-water algae, 1994).
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Similar species -->> P. angertiniense
var. duplex - var. reticulatum A cell located at the center of colonies ![]()
var. duplex
16-cells
16 = 10+5+1
Shakujii Park
Tokyo, 2001![]()
var. duplex
16-, 8-cells
16 = 10+5+1
Japan, 1997![]()
var. duplex
32-, 16-cells
16 = 10+5+1
Tochigi, 2001![]()
var. duplex
32-, 16-, 8-cells
16 = 10+5+1
Japan, 1998![]()
var. duplex
stock Smt-51
16 = 10+5+1
Minuma-tanbo
Saitama, 2001![]()
var. duplex
Nasu
Tochigi, 2001![]()
var. duplex
-cells
Wan-park-land
Kochi, 2002![]()
var. duplex ?
stock Tna-32
Nasu
Tochigi, 2001![]()
var. duplex ?
16 = 10+5+1
Tokyo, 2001![]()
var. duplex ?
16 = 10+5+1
Daidarabotchi-ike
Iizuna-kogen
Nagano, 2003![]()
var. duplex
32 = ??+1
Tama river
Komae
Tokyo, 2004![]()
var. duplex
16-cells
16 = 10+5+1
near Town Hall
Shobu
Saitama, 2004![]()
var. duplex ?
colony 54 μm φ
near Okubo ike
Shinano
Nagano, 2004![]()
var. duplex
32-cells
32 = 15+10+6+1
Kejo-numa 1
Osaki
Miyagi, 2006![]()
var. reticulatum ?
16-cells
Yamaguchi Univ.
Yamaguchi, 2004![]()
var. reticulatum
16-cells
riverside park
Abukuma river
Fukushima, 2005![]()
var. reticulatum
8-cells
Showa-machi g.p.
Showa
Saitama, 2006