oogonia; outer spore wall echinate; 31.5-32-(33)/i in diameter. 

 Antheridia 10-12- ( 13 )/i in diameter, 13-17/a long. 



This species should be compared with the larger Oe. australe (G. 

 S. West) Ti£Fany. 



Attached to submerged logs; widely distributed. Mich., Wis. 



Oedogonium taphrosporum Nordstedt & Hirn in Hirn 1900, p. 133 



Macrandrous; dioecious. Vegetative cells cylindric, 25-3S/X in 

 diameter, 100-375/a long. Oogonia 1-6; obovoid or obovoid-ellipsoid; 

 opening by a superior pore; 70-83/x in diameter, 81-1 13)U. long. 

 Oospores globose or ellipsoid-globose; outer spore wall scrobiculate; 

 58-65/x in diameter, 62-70fjL long. Antheridia 24-32/a in diameter, 

 8-12/x long. 



Mich. 



Oedogonium Tiffanyi Ackley 1929, p. 304 



PI. 43, Figs. 6, 7 



Macrandrous; dioecious. Vegetative cells cylindric, (15)-21-24/x 

 in diameter, 100-240/* long. Oogonia solitary (sometimes 2); 

 subdepressed-globose; opening by a superior pore; 64-76;u in diam- 

 eter, 65-69;a long. Oospores globose; nearly filling the oogonia; outer 

 wall smooth; median wall scrobiculate; 54-65jLt in diameter, 55-66/x 

 long. Antheridia 19-21/i, in diameter, 14-20;u, long. 



Mich. 



Oedogonium urceolatum Nordstedt & Hirn in Hirn 1900, p. 293 



PI. 33, Figs. 9, 10 



Macrandrous; dioecious (?). Vegetative cells cylindric, (24)-25- 

 {SO)ix in diameter, 80-200- ( 210 )/* long. Oogonia solitary; oblong- 

 elHpsoid, in some obpyriform; opening by a superior pore; (53)-57- 

 (70)fji in diameter, 79-82-(125)/x long. Oospores ellipsoid; filling 

 the lower part of the oogonia; middle layer of spore wall with about 

 20 longitudinal ribs, interrupted and anastomosing in our specimens; 

 (48)-54-60;a in diameter, 57-60- ( 70 )/x long; male filaments not 

 observed. 



This plant should be compared with Oe. murgaritiferum Nordst. 

 & Hirn. The irregularly inflated oogonium and the shape of the 

 oospore, together with the dimensions, are characters which agree 

 with Oe. urceolatum and which separate it from Oe. margaritiferum. 

 It is larger than Oe. Boscii, also a dioecious species. 



Attached to grass in small ponds. Wis. 



[175] 



