OED O'EO NIU M 71 
15a. Form interjectum Hirn. 
(Pl. XIII, fig. 127.) 
1900, p. 86, Pl. III, fig. 21. 
Pore of oogonium more nearly superior than in the type; vegetative 
cell 19-29 xX 60-190u; oogonium 45-60 X 63-81; oospore 44-58 & 43-58 u. 
England, Sweden. 
15b. Form pulchellum (Hassall) Hirn. 
(Pl. XIII, fig. 126.) 
1900, p. 86, Pl. III, fig. 20; Vesiculifera pulchella Hass. 1845, p. 199, Pl. 50, 
HISer oe 
Vegetative cell 25-37 X40-125u; oogonium 57-73 X68-78y; oospore 
56-66 X 56-66. 
England, France. 
15c. Var. carbonicum Wittrock. 
(Pl. XIII, fig. 128-) 
In Wittr. and Nordst. Exs. 1883; Oe. carbonicum Wittr. 1874, p. 33; Hirn 1900, 
p. 87, Pl. IV, fig. 22; Tiffany 1926, p. 90, Pl. I, fig. 5; P. B. A. No. 1781. 
Oogonium 1-2, obovoid to globose-ovoid, pore nearly superior; 
oospore obovoid-ellipsoid to globose-ellipsoid; female vegetative cell 
14-30 X40-200u, male 14-25x40-150u; oogonium 42-56 50-80y; 
oospore 40-52 X 46-65; antheridium 13-20 X 12-15n. 
United States: Iowa, Illinois, Ohio; Austria, England, 
Denmark, Germany, Sweden. 
15d. Var. minus Lemmermann. 
(Pl. XIII, fig. 129.) 
1909, p. 191, as v. minor; Heering 1914, p. 194; Tiffany 1926, p. 90, Pl. I, fig. 8. 
Oogonium and oospore smaller; female vegetative cell 16-28 
25-754, male 14-23X25-75u4; oogonitum 30-45X35-50u; oospore 
28-42 X 28—40u; antheridium 12- 15 5" —6u. 
United States: Iowa, Kentucky; Germany. 
The ‘‘cardiacum’”’ group is rather variable, and the varieties 
are not always clearly separated. The differentiating characters 
used in the key are those including shape and size of oospore 
and relative lengths of vegetative cells. Upon these bases the 
divisions above seem tenable. See also Oe. glabrum (No. 17). 
16. Oe. franklinianum Wittrock. 
(Pl. XIII, fig. 131.) 
In Wittr. and Nordst. Alg. Exs. No. 309, 1880; Wolle 1887, p. 89, figs. 7-9 
Hirn 1900, p. 88, Pl. II, fig. 18; Collins 1909, p. 231; ae 1914, p. 194; Tiffany 
1926, p. 89, Pl. IV, figs. 43-44. 
Dioecious, macrandrous; oogonium 1, subglobose, with a supra- 
median pore; oospore globose, almost filling oogonium, spore wall 
