THE GREEN ALGAE OF NORTH AMERICA 233 



Alg. Exsicc., No. 20. Monoecious ; oogonia single, oboviform or 

 suboboviform-globose, pore superior ; oospore globose or sub- 

 globose, not quite filling the oogonium, membrane smooth, 

 usually thick ; antheridium up to 4-celled, subepigynous or 

 hypogynous ; spermatozoids binate, division horizontal ; basal 

 cell elongate. 



veg. cell, 20-30 fj. diam., iK-4 diam. long. 



oog., 40-55 M " 45-65 M long. 



oos., 35-50 /x " 35-52 n " 



auth. cell, 17-24,0. " 6-ir fj. " 



Mass. Europe, Asia. 



Resembling Oc. fragile, but with vegetative cells stouter 

 and shorter, while the oogonia are of about the same size. 



12. OE. PLAGIOSTOMUM var. GRACIUUS Wittrock, 1878, p. 

 142; Hirn, 1900, p. 101, PI. VI, fig. 40. Dioecious; oogonia 

 single, oboviform-globose, pore superior ; oospore globose or 

 sub-globose, about filling the oogonium, with thick, smooth 

 membrane ; male plant about the same size as the female ; 

 antheridia i-5-celled, often alternating with vegetative cells; 

 basal cell elongate. 



veg. cell, female, 20-25 /"diam., 2-3^ diam. long. 



veg. cell, male, 20-23 /" " 2 ~4 " " 



oog., 36-42;* " 46-57 M long. 



oos., 34-39-" " 36-44 M " 



anth. cell, 19-22,". " 7-10 M " 



N. Y., Mexico. 



The type, with vegetative cells about 2 ^ thicker, oogonia and 

 oospores 7 /j- more diam., occurs in Europe; the dimensions 

 given above are for Mexican specimens ; those from Ithaca, 

 N. Y., have cells a little more slender. 



13. OE. FOVEOLATUM Wittrock, 1878, p. 133; Hirn, 1900, 

 p. 106, PL VII, fig. 46. Monoecious; oogonia single, rarely 2, 

 oboviform- or subellipsoid-globose, pore superior ; oospore glo- 

 bose or subellipsoid-globose, filling or not quite filling the oogo- 

 nium, membrane double, outer with net-like markings, inner 

 smooth ; antheridia i-7-celled, hypogynous, subepigynous, or 

 scattered ; spermatozoids binate, division horizontal ; basal cell 

 elongate, terminal cell obtuse. 



veg. cell, 14-23 M diam., 2^-5 diam. long, 



oog., 37-49 M " 38-57 ji long, 



oos., 33-46 M " 34-48 M " 



anth. cell, 15-19 M " 8-12 M " 

 St. Thomas. So. America. 



