264 TUFTS COLLEGE STUDIES, VOL. II, No. 3 



Oe. obtruncatum var. oblatum Tilden, though the dimensions 

 vary somewhat, being 



veg. cell, 15-20 /j. diam., 1/4-2% diam. long. 



oog., 37-42 M " 35-38 /ilong. 



68. OE. PLATYGYNUM Wittrock, i872a, p. i ; Wolle, 1887, p. 

 75, PI. LXXVII, figs. 1-4; Him, 1900, p. 276, PI. XLVII, fig. 

 301 ; Wittr., Nordst. and L,agerh., Alg. Exsicc., No. 1218. 

 Dioecious, nannandrous, gynandrosporous and idioandrospor- 

 ous ; oogonia single or very rarely 2, depressed-oboviform, with 

 7-12 rounded prominences arranged in a whorl around the middle, 

 operculate, division inferior ; oospore depressed- or subde- 

 pressed-globose, not quite filling the oogonium, membrane 

 smooth ; suffultory cell not or slightly swollen ; androsporangia 

 i -3 celled; vegetative cells slightly capitellate, terminal cell 

 obtuse ; dwarf males unicellular, oboviform, ve^ small, on the 

 oogonium. 



veg. cell, 

 oog., 

 oos., 



andr. cell, 

 nan. cell, 



N. J., Pa., Fla., Minn. Europe, So. America. 



The peculiar form of the oogonium, with the whorl of projec- 

 tions, is not found in any other American species. 



69. OE. PLUVIALE Nordstedt in Rabenhorst, Algen., No. 

 2257; Him, 1900, p. 280, PI. XLVIII, fig. 311 ; P. B.-A., No. 

 1190. Oe. fonticola Wolle, 1887, p. 93, PL L,XXV, figs. 4-6. 

 Dioecious, nannandrous, idioandrosporous ; oogonia single, very 

 rarely 2-3, oboviform-globose or subglobose, operculate, divi- 

 sion superior ; oospore subglobose or subellipsoid-globose, 

 almost filling the oogonium, membrane smooth ; suffultory 

 cell not swollen ; vegetative cells varying much in diameter in 

 the same individual ; basal cell elongate, terminal cell obtuse ; 

 androsporangial plants often somewhat more slender than the 

 female ; androsporangia to lo-celled ; dwarf males broadly 

 oboviform, unicellular, on the oogonium. 



veg. cell, female, 22-29 v- diam., ^-2 diam. long, 



veg. cell, male, 18-27 f- " 1-2 " " 



oog., 34-45 M " 34-50 /* long, 



oos., 32-40 n " 31-43 p 



andr. cell, 17-25 M " 6-13 n " 



nan. cell, 10 /x " 14- ISM " 



Cal. Europe. 



