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



often alternating ; spermatozoids binate, division vertical ; vege- 

 tative cells varying much in diameter in the same filaments ; 

 suffultory cells often larger and shorter than the others ; basal 

 cell elongate, terminal cell obtuse. 



veg. cell, 13-20 M diam., 4-8 diatn. long. 



oog., 45-5O M " 66-100 /a long. 



COS., 42-47 M " 60-75 M " 



anth. cell, 15-18 M " 7-10 /u " 



Greenland, N. H., Michigan. Europe. 



A special character of this species is the variation in size of 

 the cells in the same filament. The cells under the oogonia are 

 the stoutest and shortest, those directly over the oogonia the 

 longest and most slender. The antheridial cells are very sel- 

 dom over 2 in a series. 



18. OE. RICHTERIANUM I,emmerman, 1895, p. 26, figs. 

 1-3; Him, 1900, p. 117, PI. XII, fig. 63 ; P. B.-A., No. 1429. 

 Monoecious ; oogonia single or 2, oboviform or subellipsoid, 

 pore superior ; oospore suboboviform or subellipsoid, rarely 

 globose-ellipsoid, quite or nearly filling the oogonium, mem- 

 brane smooth; antheridia i-6-celled, subhypogynous, subepi- 

 gynous or scattered ; spermatozoids binate, division horizontal ; 

 basal cell usually elongate. 



veg. cell, 12-21 M diam., 3-6^ diam. long, 



oog., 36-48 /x " 48-74 Mlong. 



oos., 35-43 M " 43-59 M " 



anth. cell, 12-15 M " 6-9 M " 



Mass. Europe. 



19. OE. RIVULARE (LeCl.) A. Braun, i855a, p. 23, PI. I, 

 figs, i-ie; Wolle, 1887, p. 92, PI. LXXXIII, figs, i and 2 ; 

 Hirn, 1900, p. 119, PI. XII, fig. 66; Phyk. Univ., No. 70. 

 Dioecious; oogonia single or 2-7-seriate, oboviform, pore 

 superior ; oospore oboviform, ellipsoid or subglobose, not nearly 

 filling the oogonium, membrane smooth; male plant somewhat 

 more slender than the female ; antheridia to i3-celled ; sperma- 

 tozoids binate, division horizontal ; basal cell elongate. 



veg. cell, female, 35-45 /x diam., 3-8 diam. long. 



veg. cell, male, 30-3611 " 4-8 " " 



oog., 70-85/11 " 130-160 /x long. 



oos., 55-yo/i " 65-10011 " 



anth. cell, 21-28 M " 14-26 /u " 



Iowa, Florida. Northern Europe. 



A large species, easily recognizable by the size, the oogonia 

 many in a series, and the oospore much smaller than the oogo- 



