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OEDOGONIUM 93 
57a. Form cylindricum Hirn. 
(Pl. XXVIII, fig. 244.) 
1900, p. 129, Pl. XV, fig. 85; Oe. boscu (Le Cl.) Wittr. in P. B. A. No. 118, 1895. 
Oogonium and oospore cylindric-oblong or more rarely ellipsoid or 
obovoid-ellipsoid; ribs of vospore scarcely crenulate; vegetative cell 
11-16 X44-150y; oogonium 30-36 X42-81lyu; oospore 27-34 K 4065p. 
United States: Massachusetts, Connecticut, Missouri, Illi- 
nois, New Hampshire. 
57b. Var. aureum Tilden. 
(Pl. XXVIII, fig. 245.) 
In Amer. Algae, Nos. 123 and 186, 1896; 1898, p. 90, PI. 8, figs. 1-3; Hirn 1900, 
Pl. XV, p. 130, fig. 87. 
Oospore obovoid to globose-ellipsoid, not completely filling oogonium, 
middle spore wall with dentate ribs (sometimes nearly areolate); 
vegetative cell 10—-13X35-110y; oogonium 30-35X38-50u; oospore 
29-33 X 35-43yu; antheridium 10 10x. 
United States: Colorado. 
57c. Var. longiarticulatum Hansgirg. 
(Pl. XXVIII, figs. 242 and 243.) 
1888, p. 46; Oe. calosporum Hirn 1895, p. 20, Pl. 1, fig. 3; Hirn 1900, p. 130, 
Pl. XV, fig. 86. 
Oogonium single; oospore obovoid to nearly ellipsoid, not filling 
oogonium, ribs of median layer of spore wall distinctly crenate; veg- 
etative cell 12-15 60—-90y; oogonium 27-30 58—0u; oospore 24-27 X 
44-52y. 
United States: Michigan, Massachusetts; Austria, Finland; 
Brazil. 
There exists considerable variation in the members of the 
crenulatocostatum group. ‘The crenate or crenulate ribs (some- 
times nearly smooth), the usually seriate oogonia, and small 
size are characteristic. Cf. Oe. exocostatum (No. 50). The 
variety aureum has dentate ribs which sometimes appear nearly 
areolate. It is felt, after examining hundreds of specimens of 
this group, that the above form and varieties are usually 
sufficiently distinct to be recognized. Ecological variants are 
common and to give varietal distinction to each of these is 
merely to make a difficult situation worse. Plants of longzarit- 
culatum from Brazil are slightly smaller in all dimensions than 
those given above (Borge). 
