OEDOGONIUM 99 
Oe. paucocostatum is characterized among the species with 
ellipsoid oogonia and longitudinally ribbed oospores by the 
~ small number of ribs and by its relatively smaller dimensions. 
Its nearest relative is the larger Oe. australianum (No. 72). 
72. Oe. australianum Hirn. 
(Pl. XXXII, figs. 283 and 284.) 
1900, p. 192, Pl. XX XI, fig. 192. 
Dioecious, macrandrous; oogonium 1-2, ellipsoid, operculate, 
division superior; oospore ellipsoid or globose-ellipsoid, practically 
filling oogonium, median layer of spore wall longitudinally ribbed, ribs 
17-23, sometimes anastomosing; antheridium to 6-seriate; vegetative 
cell 17-22 X 70-170; oogonium 59-74 X 74—96u; oospore 56-70 X 59-74y; 
antheridium 14-16 10-15u. 
Australia. 
Cf. Oe. paucocostatum, above. 
73. Oc. tumidulum (Kuetzing) Wittrock. 
(Pl. XXXII, figs. 281 and 282.) 
1874, p. 35; Conferva tumidula English Botany No. 1670 in Kuetz. Dec. Alg. 
No. 60, 1833: Hirn 1900, p. 191, Pl. XX XI, fig. 191. 
Dioecious, macrandrous; oogonium 1, subellipsoid, operculate, 
division superior; oospore ellipsoid or globose-ellipsoid, quite filling 
oogonium, outer layer of spore wall with 40—50 longitudinal ribs granu- 
late and sometimes anastomosate, inner layer smooth; antheridiurn to 
45-seriate; sperms 2, division horizontal; vegetative cell, female 18-25 
65-125u, male 15-20X60-120u; oogonium 52-63X78-90u; oospore 
49-58 X61—75u; antheridium 15-20 9-15un. 
Germany. 
Oe. tumidulum is the only dioecious, macrandrous member of 
the genus having the combination of subellipsoid oogonia with 
superior pore and more than 40 longitudinal ribs on the oospore. 
Cf. the monoecious Oe. insigne (No. 75). 
74. Oc. nobile Wittrock. 
(Pl. XXXII, fig. 279.) 
1874, p. 14; Hirn 1900, p. 189, Pl. XXX, fig. 188. 
Monoecious; oogonium 1 (very rarely 2); ellipsoid or subobovoid- 
ellipsoid, operculate,. division superior; oospore ellipsoid-globose or 
globose, not filling oogonium, spore wall of three layers: outer layer 
‘smooth, middle layer with 30-35 continuous longitudinal ribs, rarely 
anastomosate, inner layer smooth; antheridium 1-3, hypogynous; 
sperms 2, division horizontal; vegetative cell 16-20 x 80—180u; oogonium 
57-65 X 67-90u; oospore 48-55 50—-58u; antheridium 15-19X9-13uy. 
Norway. 
