OEDO GON LUM 
ax 
On 
zigzag rarely has more than 6-8 cells in the filament. Skuja 
(1927) also records the membrane of the vegetative cell as 
being spirally punctate. 
24. Oc. fragile Wittrock. 
(Pl. XV, fig. 145.) 
1870, p. 120; 1872a, p. 24; Wolle 1887, p. 71, Pl. 74, figs. 4-6; Oe. Candollei (Le 
Cl.) Breb. in Roumeguere Alg. Exs. No. 347; Hirn 1900, p. 96, Pl. V, figs. 33 and 34; 
Collins 1909, p. 232, fig. 81; Heering 1914, Pl. IV, fig. 36; P. B. A. No. 1477. 
Monoecious; oogonium 1, globose or subobovoid-globose, with 
superior pore; oospore globose, filling oogonium, spore wall smooth; 
antheridium 1-8; sperms 2, division horizontal; basal cell elongate; 
vegetative cell 12-17X50-120u; oogonium 42-5044-55yu; oospore 
39-46 X 39—-46u; antheridium 12-15 10—-12u. 
United States: Iowa, Illinois, Mississippi, Massachusetts, 
Pennsylvania, Michigan; British Columbia; Patagonia; South 
Africa; Australia; France, Finland, Sweden, Latvia. 
24a. Var. abyssinicum Hirn. 
(Pl. XV, fig. 147.) 
1900, p. 97, Pl. VI, fig. 35. 
Oogonium smaller than the type; antheridium to 6-seriate; veg- 
etative cell 12-17 X 25-100; oogonium 38-45 X 40—50y; oospore 36-43 X 
36-44; antheridium 11-15x6-14uy. 
Africa. 
24b. Var. robustum (West and West) Tiffany nov. comb. 
(Pl. XV, fig. 146.) 
Oe. zigzag Cleve var. robustum West and West 1903, p. 36; zbid. in West 1904, 
p. 60, fig. 12B; cbid. in Hirn 1906, p. 24, Pl. I, fig. 3. 
Oogonium usually globose; antheridium 2; vegetative cell 19-23 
40—90u; oogonium 53-58 X50- 60u; oospore 51— 56X47- ues antheridium 
19 5-7. 
England. 
Oe. fragile is characterized by its usually globose spores 
completely filling the oogonia, its size, and monoecious habit. 
Cf. Oe. globosum (No. 21) and Oe. intermedium (No. 19). The 
variety abyssinicum is more slender and has a larger number 
of seriate antheridia than the species. Variety robustum 1s 
considerably larger than either. The latter was. originally 
described by W. and G. S.- West as a variety of Oe. zigzag 
(No. 22). Its pluricellular habit and number of antheridia 
place it outside the few-celled zzgzag. Its globose oospore 
completely filling the oogonium and its subepigynous and 
subhypogynous antheridia are characters that seem nearest to 
Oe. fragile. 
