98 THe Of pOGONnas On Awe 
vegetative cell 25-38 xX 100-375u; oogonium 70-83 X81-113yu; oospore 
58-65 X 62-70u; antheridium 24-32 < 8-12u. 
United States: Massachusetts, Michigan, Illinois; Brazil; 
India; Columbia. 
This species is readily recognized by its large size and its 
scrobiculate oospore, the latter not filling the oogonium. West 
(1914) recorded the alga from Columbia with vegetative cells 
19-22u in diameter, and with oogonia and oospores slightly 
smaller than the dimensions given above. 
70. Oe. pseudacrosporum Wittrock. 
(Pl. XXX, figs. 268 and 269.) 
In Hirn 1900, p. 193, Pl. XXXII, fig. 196. 
Monoecious; oogonium 1, ellipsoid, operculate, division supreme, 
lid very small and often deciduous; oospore ellipsoid, completely filling 
oogonium, spore wall coalescing with that of oogonium, longitudinally 
ribbed, ribs evidently crenulate; antheridium 1-4, hypogynous or sub- 
epigynous; sperms 2, division horizontal; basal cell elongate; terminal 
cell long, setiform; vegetative cell 9-1332-110u4; oogonium ‘(27-) 
32-37 X (40—) 45-56u; antheridium 8-10 6-10uy. 
United States: Iowa, Florida; Sweden. 
Its monoecious habit, supreme operculum, and ribbed 
oospore are characteristic. It should be compared with the 
nannandrous Oe. acrosporum (No. 195). 
71. Oe. paucocostatum Transeau. 
(Pl. XXXII, fig. 277.) 
1914, p. 300, Pl. XXVIII, fig. 5; Collins 1918, p. 66; Tiffany 1926, Pl. V, figs. 
55 and 56. 2 
Dioecious, macrandrous; oogonium 1, ellipsoid, operculate, division 
superior; oospore ellipsoid, nearly filling the oogonium, outer wall 
smooth, median wall longitudinally ribbed, ribs 15-19 in number, inner 
wall smooth; antheridium 2-8, sperms 2, division horizontal; terminal 
cell obtuse, basal cell usually elongate; vegetative cell, female (15—) 19-25 
70-1604; oogonium 54-60 X 70-104u; oospore 50-56 X 66—-90u; anther- 
idium 18-23 x 8-12u. 
United States: Illinois, Iowa, Ohio. 
7la. Var. gracilis Tiffany. 
(Pl. XXXI, fig. 278.) 
1921, p. 273; 1926, p. 99. 
Somewhat smaller than the species, oospore ellipsoid or occasionally 
globose-ellipsoid, completely filling the oogonium or not filling the 
oogonium; otherwise similar to the type; vegetative cell 15-20 x 66-120; 
oogonium 48-52 x 70-88; oospore 44-48 X 60-704; antheridium 17-20 X 
8-12u. 
United States: Ohio, Iowa. 
