OED OGONILUM 89 
Longer vegetative cells; oogonium and oospore larger than in type; 
vegetative cell, female 42-50X120-250u, male 40-48X120-240,; 
oogonium 75-85X96-1374; oospore 67-79X84-100u; antheridium 
34-45 X 7-1du. 
Brazil; South Africa. r 
For a discussion of the chief characteristics of the crassum 
group, see notes under Oe. landsborought (No. 48). The variety 
- amplum is larger than the species proper and has shorter 
vegetative cells than the variety subtumidum. Fritsch’s form 
of crassum from South Africa is nearest the variety subtumidum. 
The variety Jongum is readily characterized by its elongated 
oogonia and oospores. 
50. Oe. exocostatum Tiffany. 
(Pl. XXVII, figs. 235-237.) 
1921, p. 272, Pl. I, figs. A-F, 1926, p. 94, Pl. V, figs. 51-54. 
Dioecious, macrandrous, oogonium 1-2, ellipsoid to ellipsoid- 
globose, occasionally terminal, pore superior; oospore of the same form 
as the oogonium, which it very nearly completely fills, spore wall of two 
layers: the outer marked by 13-15 longitudinal ribs, inner smooth; 
suffultory cell swollen; male filament a little more slender than the 
female, antheridium 3-7; sperms 2, division horizontal; basal cell 
elongate; female vegetative cell (138—) 18-25 x 72-140, male (13—) 16-20 
<48-100u; suffultory cell 22-3060-90u; oogonium 40-52 60-96y; 
oospore 38-41 X 56-68; antheridium 12-16 X7-12uy. 
United States: Iowa, Ohio. 
This species is readily distinguished by the presence of 
longitudinal ribs on the outer layer of the oospore wall. Other- 
wise it is similar in appearance to Oe. crenulatocostatum (No. 57). 
51. Oc. kjellmanii Wittrock; Hirn. 
(Pl. XXVI, fig. 223.) 
1900, p. 127, Pl. XIV, fig. 82; Wittr. 1880, 71 Wittr. and Nordst. Alg. Exs. 
No. 306. 
Dioecious, macrandrous; oogonium 1, cbovoid or rarely subellipsoid, 
pore superior; oospore ellipsoid or subellipsoid, not completely filling 
oogonium, spore wall of 3 layers: outer layer internally ribbed, middle 
layer with 35-45 slightly crenulate longitudinal ribs, anastomosate, 
inner layer smooth; antheridium to 30-seriate; sperms 2, division 
vertical; female vegetative cell 15-22 45-120u; male 14-18 56-120y; 
oogonium 41-50 x 60—75y; oospore 39-47 48-57; antheridium 12-15 X 
4—12u. 
Borneo. 
Characterized by the large number of longitudinal ribs on 
the middle layer of the oospore. 
