CEDOGONIUM. 75 



Diameter veg. cells, 3-5 yu ; 5-6 times longer. 

 Diameter oogon., 14-16 yw by 34-42 yw. 

 Diameter oospor. , 13-15 ju by 24-31 yu. 

 Diameter sperm, cells, 3-3] yw by 4 yw. 



Ponds, Pennsylvania. 

 Plate LXXV, fig. 2. 



SECTION II. DIOECIOUS SPECIES. 



- 



SUBSECTION I. SPECIES WITH DWARF MALES. 



A. Species with dwarf males unicellular, 

 a. Oogonia vertically constricted. 



OEDOGONIUM PLATYGYNUM, Wittr. 



Gynandrosporous, oogoiiia single, rarely binate, depres- 

 sedly obverse egg-shaped; constrictions 7-12, angles 

 rounded; oogoiiia cut round (circumsclssile) below the 

 middle, opening by a pore seated in the fissure, vertical view 

 orbicular, margin sinuate with depressions corresponding 

 with the constrictions ; oospore somewhat depressed-globose 

 nearly filling the oogonium aiidrosporangia 1-3 celled; 

 terminal cell obtuse ; dwarf males small, obverse egg-shaped, 

 seated on the oogoiiia. 



Diameter veg. cells, 6-8 yw ; 2-5 times longer. 

 Diameter oogon., 21-30 yu by 16-24 //. 

 Diameter oospor., 17-24 yu by 15-20 yw. 

 Diameter androsp. cells, 6-8 yu by 7-8 yw. 

 Diameter of dwarf males, 4-5 yw by 8-9 yw. 



Frequent in ponds, New Jersey, Florida, Minnesota. 

 Plate LXXVII, figs. 1, 2, filaments ; figs. 3, 4, transverse 

 sections of oogoiiia. 



b. Oogonia destitute of vertical constrictions. 



I. Oospore globose or subglobose. 



OEDOGONIUM DECIPIENS, Wittr. 



Gynandrosporous, oogoiiia single or two or three in series ; 

 depressed-globose, narrowly circumcised in middle, open- 

 ing by a pore in the fissure ; oospore depressed-globose, not 



