248 TUFTS COLLEGE STUDIES, VOL. II, No. 3 



brane smooth, often thick ; antheridia i-3-celled, subepigynous 

 or hypogynous ; spermatozoids binate, division horizontal ; 

 vegetative cells with two undulate constrictions ; basal cell 

 elongate, not constricted ; terminal cell obtuse or apiculate. 



veg. cell, 20-29 P diam., i/^-4/^ diatn. long. 



oog., 48-57 <" " 56-73 . M long. 



oos., 46-53 M " 49-5 6 M " 



anth. cell, 18-25 /u, " 7-9 fj. " 



The type occurs in Europe, Asia, Australia, and So. America, 

 but has not been reported from No. America ; but we have 



Var. COMMUNE Him, 1900, p. 187, PI. XXX, fig. 185; P. 

 B.-A., No. 74, as Oe. nodulosum. Oogonia and oospores larger, 

 the former suboboviform-ellipsoid to ellipsoid, more rarely 

 globose-ellipsoid. 



veg. cell, 22-29 /" diam., iK-4/^ diam. long, 



oog., 64-74^ " 70-90 /along. 



oos., 56-70 M " 67-80 /j. " 



anth. cell, 18-26 M " 7-10 //. " 



Mass. Finland. 



The specific name is due to the constrictions in the vegetative 

 cells, each cell appearing to consist of three parts, separated by 

 necks. No other American species has this character. 



42. OE. NOBILE Wittrock, 1874, p. 14; Hirn, 1900, p. 189, 

 PI. XXX, fig. 188. Monoecious; oogonia single, very rarely 

 2, ellipsoid or suboboviform-ellipsoid, operculate, division 

 superior ; oospore ellipsoid-globose or globose, not filling the 

 oogonium, membrane triple ; outer membrane smooth, median 

 membrane with 30-35 continuous longitudinal lines, rarely anas- 

 tomosing, inner membrane smooth ; antheridia i-3-celled, hypo- 

 gynous ; spermatozoids binate, division horizontal. 



veg. cell, 16-20 /j. diam., 5-9 diam. long. 



oog., 57-65 M " 67-90 M long. 



oos., 48-55^ " 67-79 /u. " 



anth. cell, 18-19 /u " 9-13 n " 



The dimensions given are of the type occurring in Norway ; 

 the American form, occurring in Mass., has dimensions as 



follows : 



veg. cell, 14-20 fj. diam., 6-n diam. long. 



oog., 57-63 M " 81-95 ^ long. 



oos., 55-60 M " 67-79^ " 



anth. cell, 14-19 M " 13-17 M " 



As the characters otherwise agree, the form does not seem to 

 require a special name. This species has the spore membrane 



