102 THE OF DOCON TNE BOE 
79a. Var. minus Tiffany. 
(Pl. XXXIII, fig. 294.) 
1927, p. 204, Pl. IX, figs. 6 and 7 (as v. minor). 
Smaller than the type; vegetative cell 7-9 x 27-48yu; oogonium 26-29 
X28-36u; oospore 24—-26X24—-26u; antheridium 7-8X10—-12u; basal 
cell 12-14 X 10-12. 
United States: Illinois. 
Oe. howardi has broadly capitellate vegetative cells as in 
Oe. infimum (No. 78) and Oe. inversum (No. 77), but differs 
from both in the median position of its operculum. It is 
perhaps nearest Oe. latiusculum (No. 81), the latter being 
larger and possessing a very wide division of the oogonium. 
The variety minus is characterized chiefly by its smaller size 
and subspherical basal cell. 
80. Oe. pratense Transeau. 
(Pl. XXXIV, figs. 298 and 299.) 
1914, p. 297, Pl. XXIX, figs. 9-12; Collins 1918, p. 66; Tiffany 1926, p. 96, 
Pivstisss l0vand tal: 
Dioecious, macrandrous; oogonium 1 (rarely 2), subdepressed- 
globose or broadly pyriform-globose, operculate, division median, 
narrow but distinct; oospore depressed-globose or subglobose, filling or 
nearly filling oogonium, spore wall smooth; antheridium 1-2, usually 
alternating with vegetative cell; sperm 1; basal cell elongate; vegetative 
cell, female 10—-17X35—-95y, male 8-15X32-82u; oogonium 33-40 
35-50; oospore 32-88 X 28-35u; antheridium 10-14 13-18u. 
United States: Illinois, Iowa, Ohio, Alabama, Mississippi, 
Michigan. 
Oe. pratense is distinguished from Oe. latiusculum below by 
the narrow opening of the operculum and by its cylindrical 
vegetative cells. The latter character together with its larger 
size separates it from Oe. howardit (No. 79). The basal cell of 
Oe. pratense is uniformly elongate. Among the monoecious 
forms it bears some resemblance to Oe. acmandrium (No. 82) 
and Oe. psaegmatosporum (No. 83). 
Sl. Oe. latiusculum Tiffany. 
(Pl. XXXIII, figs. 287 and 288.) 
1924, p. 182, Pl. III, figs. 4-6; 1926, p. 96, Pl. VI, figs. 72-74. 
Dioecious, macrandrous; oogonium 1-2, globose to ellipsoid-globose; 
oogonium operculate, division median, very wide; oospore of the same 
form as the oogonium which it very nearly or completely fills, wall 
smooth; male plant somewhat larger than the female; antheridium 1, 
usually alternating with a single vegetative cell, sperm 1; vegetative 
cell distinctly capitellate; basal cell of filament subhemispherical, not 
elongated; filament not infrequently incrusted with lime; female veg- 
