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



Oe. obtnincatum var. oblatum Tilden, though the dimensions 

 vary somewhat, being 



veg. cell, 15-20 /j. diani., 1/4-2)4 diatn. long. 



oog., 37-4- M " 35-38 Along. 



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

 75, PL 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 

 1-3 celled ; vegetative cells slightly capitellate, terminal cell 

 obtuse ; dwarf males unicellular, oboviform, very small, on the 

 oogonium. 



veg. cell, 6-10 /j. diam., 2-5 diatn. long, 



oog., 21-30 /j. 16-24 A 4 long, 



oos., 17-24 M " 15-20 n " 



andr. cell, 6-8 ^ " 7-8 ^ "' 



nan. cell, 4.5-5 P. " 8.5-9.5 M " 



X. 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 Rabeuhorst, Algen., No. 

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

 1190. Oe. fonticola Wolle, 1887, p. 93, PI. I V XXV, figs. 4-6. 

 Dioecious, nannandrous, idioandrosporous ; oogonia single, very 

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

 sion superior ; oospore subglobose or subellipsoid-globose, 

 almost rilling 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., 5 4 -2 diam. long, 



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



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



oos., 32-40 M " 3 ! -43M " 



aiidr. cell, 17-25 ^ " 6-13 /j. " 



nan. cell, 10 n " l 4-*5 M " 



Cal. Europe. 



