THE GREEN ALGAE OF NORTH AMERICA 259 



oogonia single or 2, more rarely 3, oviform or ellipsoid, oper- 

 culate, division superior ; oospore ellipsoid, about filling the 

 oogonium, membrane sometimes very finely crenulate ; sufful- 

 tory cell similar to other vegetative cells ; basal cell elongate, 

 terminal cell obtuse ; dwarf males on the oogonium ; anther- 

 idium exterior, i- (or more-) celled, curved. 



veg. cell, 4-7 fj. diam., 2-5 diam. long, 



oog., 16-18^ " 21-25 M long, 



oos., 15-17 M " 17-19 /j. " 



nan. stipe, 5-6 M " 10-15 /* " 



anth. cell, 4-5 M " 5-6 M " 



Mass., Pa. Europe. 



A very slender species, usually found as scattered filaments 

 among other species of Oedogonium. The curved antheridia 

 seem peculiar among the American species. 



62. OE. ACROSPORUM De Bary, 1854, pp. 47, 60, 94, PI. Ill, 

 figs. 1-12; Hirn, 1900, p. 244, PI. XLI, fig. 254; Oc. acro- 

 spontm var. connectcns P. B.-A., No. 409. Dioecious, nannan- 

 drous, gynandrosporous (or idioandrosporous) ; oogonia single, 

 terminal, ellipsoid, operculate, division near summit, operculum 

 minute, deciduous; membrane of oogonium with longitudinal, 

 sometimes anastomosing ridges on the inner surface ; oospore 

 quite filling the oogonium, the outer membrane with 23-30 

 longitudinal, very finely crenulate ridges, closely fitting between 

 the ridges of the oogonium, and connected by delicate trans- 

 verse striae ; inner membrane smooth ; suffultory cell somewhat 

 swollen ; basal cell elongate, terminal cell obtuse ; androspor- 

 angia i-2-celled, hypogynous ; dwarf males curved, on the suf- 

 fultory cell, stipe sometimes 2-3-celled, upper cells long, 

 antheridium exterior, i-2-celled. 



veg. cell, 13-21 fj. diam., 3-6 diam. long, 



suf. cell, 17-25 ft " i l /2-T, " " 



oog., 38-48 M " 50-63 M long, 



andr. cell, 16-21 M " 12-15 ^ " 



lower cell, nan. stipe, 9-12 ^ " 30-38 M ' 



upper cell, nan. stipe, 6-8 /x " 55-?i M 



anth. cell, 6-8 M " 9-15 ^ " 



Mass. Europe, Asia, So. America. 



Our only species of Oedogonium in which each fertile filament 

 bears one terminal oogonium, and none elsewhere. 



Forma BOREALE (Wolle) Hirn, 1900, p. 245, PI. XLI, fig. 

 256 ; Oe. acrosporum var. boreale Wolle, 1887, p. 84, PI. LXXIX, 



