THE GREEN ALGAE OF NORTH AMERICA 427 



disappearing. Though the antheridium is really terminal, it is 

 often pushed aside by the oogonium, and appears to be lateral, 

 below the oogonium. On moist ground or submerged, common. 

 Greenland, Mass., Neb., Cal. /Europe. 



There is considerable resemblance between V. tcrrcstris and 

 r. ha ma fa, but in the former the fruiting branch is short, the 

 oogonium practically sessile on the pedicel of the antheridium ; 

 in the latter the fruiting branch is usually longer and the oogo- 

 nium and the antheridium are on distinct pedicels, appearing as 

 if the branch had forked ; the manner of disappearance of the 

 oogonium membrane is different ; aplanospores are not known 

 in / '. tcrrcstris, though it is the commoner species. 



ii. V. GEMINATA (Vauch.) De Candolle, 1805, p. 62 ; Walz, 

 1866, p. 147, PI. XII, figs. 7-11 ; Wolle, 1887, p. 151, PI. 

 CXXVIII, figs. 1-3; P. B.-A., No. 1287. Filaments 50-100 /x 

 diam. ; oogonia 2, 70-90X60-75 /x, ellipsoid-hemispherical to 

 convex-concave, shortly stipitate near the end of a short branch; 

 the antheridium between them, cylindrical, hooked or circinate ; 

 ripe oospore brown-spotted with triple membrane, filling the 

 oogonium ; aplanosporangia either on the same frond as the 

 oogonia or on separate individuals, aplanospores 120- 200 X 

 120-190 /A, formed in ovoid sporangia usually terminating short, 

 lateral branches, freed by the dissolution of the membrane ; 

 akinetes formed by the breaking up of portions of the filaments 

 into short, thick-walled cells, whose development varies consid- 

 erably, according to circumstances. Common in quiet or slowly 

 running water. Greenland, Me., Mass., N. J., Neb., Cal. 



Europe. 



Var. RACEMOSA (Vauch.) Walz, 1866, p. 147 ; P. B.-A, No. 

 268. Oogonia 3-many, smaller than in the type, corymbosely 

 arranged about the antheridium. Vt., Mass., N. J., Neb., 

 Washn., Cal. Europe. 



The variety differs from the type only by the greater number 

 of oogonia, and there is no sharp division ; plants representative 

 of each can often be found in the same tuft ; the variety seems 

 to be more abundant than the type.* 



*Gbt/., 1897, p. 124, includes under V. racemosa what is above included 

 under both V. geminata and var. racemosa; and at p. 126 applies the 

 name V. geminata to what appears to be quite a different plant, and to 

 judge by the descriptions and figures a good species ; but why it should 

 bear the name of V. geminata is not so clear. His fig. 45. fhows a quite 

 regular ovoid spore ; Vaucher says that the spores of Ectosperma gemin- 

 ata "au lieu d'etre arrondies, representent une portion de sphere forte- 



