88 TT wo OsD:0 COW AC Ey AcE 
although one can scarcely confuse the two after some familiarity 
with them. The shape of the oogonia is quite similar in each, 
but the oospore is perhaps the most distinctive characteristic. 
The oospore of landsboroughit varies from ovoid to ellipsoid 
while the oospore of crassum varies from ellipsoid to nearly 
globose. Globose oospores are never present in Oe. lands- 
borought. The variety norvegicum has stouter and_ shorter 
vegetative cells. Compare also with Oe. subrectum (No. 47) 
and Oe. grande (No. 45). 
49. Oe. crassum (Hassall) Wittrock. 
(Pl. XXIII, figs. 202 and 203.) 
(?) Vesiculifera crassa Hass. 1842, p. 389; Oe. crassum Wittr. 1872a, p. 20, Pl. 1, 
figs. 4-6; Hirn 1900, p. 139, Pl. XVIII, fig. 99; Heering 1914, p. 200, fig. 286; Tiffany 
1926, p. 93, Pl. II, figs. 17 and 18. 
Dioecious, macrandrous, oogonium 1-2, ovoid to obovoid-ellipsoid, 
pore superior; oospore ellipsoid to globose, filling or not filling oogonium, 
spore walls smooth; antheridium 2-25; sperms 2, division vertical; 
female vegetative cell 36-50 X 72-340y, male 30-36 X 72-260u; oogonium 
60-78 X 85-1204; oospore 58-76 X75—-96yu; antheridium 28-32 X 10—-20uz. 
United States: Iowa, Florida, Ohio, Michigan, Mississippi, 
Alabama, Indiana; Austria, England, Germany, Sweden; South 
Africa. 
49a. Form amplum (Magnus and Wille) Hirn. 
(Pl. XXIII, figs. 204 and 205.) 
1900, p. 1389, Pls. XVIII and XIX, fig. 100; Oe. amplum Magnus and Wille in 
Wille 1884, p. 40, Pl. 2, figs. 65 and 66; Oe. crassum (Hass.) Wittr. in Wille 1884, 
p. 39, Pl. 2, fig. 64; (?) Oe. rivulare (Le Cl.) Al. Br. var. major Wolle 1887, p. 92, . 
PIiWGete. (and 8. 
Of larger dimensions; vegetative cell, female 46-54 70-160u, 
male 42-5065-200u; oogonium 75-90X83-1154; oospore 72-85X 
77-100u; antheridium 40—50 X 8—20u. 
United States: Ohio, Illinois, Mississippi, (?) Florida, Michi- 
gan; Uruguay, Brazil. 
49b. Var. longum Transéau. 
(Pl. XXIV, fig. 208.) 
1918, p. 237. 
Elongated oogonium and oospore; vegetative cell, female 40-52 
< 100-240u, male 36-44100-180u; oogonium 68-84% 120-180; 
oospore 66-80 X 100-125; antheridium 34-40 8-14u. 
United States: New York (Short Point Bay, Oneida Lake). 
49c. Var. subtumidum Hirn. 
(Pl. XXIII, figs. 206 and 207.) 
1900, p. 140, Pl. XIX, fig. 101. 
