THE GRKEN ALGAE OF NORTH AMERICA 425 



oospore globose or ovoid, with triple membrane, 75-100 p. diam., 



not filling the oogonium ; antheridia cylindric or subclavate, 



'30-40 p. diam., erect, more or less incurved, on each side of the 



series of oogonia. In ponds and ditches. Mass., Conn., Neb., 



Cal. Europe. 



The distinguishing mark for this species is found in the 



oogonia facing in opposite directions. 



5. V. DICHOTOMA (L,.) Agardh, 1817, p. 47; Walz, 1866, p. 

 152, PI. XIV, figs. 28-33 ; Wolle, 1887, p. 149, PI. CXXVI, 

 figs. 1-7; Wittr. and Nordst., Alg. Exsicc., Nos. 337, 338. 

 Dioecious, filaments 135-200 p. diam., oogonia sessile, 300-400 p. 

 diam., globose or ovoid-globose, distant or 2-6 approximate; 

 ripe oospore with triple membrane, brown spotted ; antheridia 

 erect, ovoid, 90-150X150-250^. In ponds and ditches. W. I. 



Europe. 



Recorded by Wolle without definite locality. V. Pihts Wolle, 

 1887, p. 153, PI. CXXVII, figs. 1-4, from Vt., may be a form 

 of this species. 



6. V. REPENS Hassall, i843b, p. 430; 1845, p. 52, PI. VI, 

 fig. 7; Gotz, 1897, P- IIO > fig 8 - 14-16. Filaments 33-50 p. 

 diam. ; oogonia single, rarely two, sessile, obliquely ovoid, 

 70-80X55-80 p., ending in a short beak, usually horizontal; 

 oospore quite filling the oogonium, grayish, coarse grained, 

 with triple membrane and one or more brown spots ; antherid- 

 ium close to the oogonium, circinate, on a straight or curved 

 pedicel; zoospores 80-130X75-120 p., formed in nearly cylindri- 

 cal sporangia ; cilia uniformly distributed. On moist ground 

 or submerged. Cal. Europe. 



7. V. SESSILIS (Vauch.) De Candolle, 1805, p. 63 ; Kiitzing, 

 1856, PI. LIX, fig. 2 ; Wolle, 1887, p. 151, PI. CXXVII, figs. 

 9-1 1 ; Gotz, 1897, p. in, figs. 17-22; P. B.-A., No. 228. Fil- 

 aments 50-85 p. diam.; oogonia usually two, sometimes single, 

 sessile, ovoid or oblong-ovoid, 70-85X75-100 p., more or less 

 oblique, with short beak ; antheridium between the oogonia or 

 beside the single oogonium, on a short pedicel, straight, hooked 

 or circinate ; ripe oospore dark-spotted, with triple membrane, 

 filling the oogonium ; zoosporangia ovoid-clavate, terminal on 

 a branch which is however sometimes so short that the spor- 

 angium appears sessile; zoospores 110-145X110-125 p., with 

 cilia evenly distributed. Me., Mass., R. I., Conn., N. J., Neb., 

 Alaska to Cal. Europe. 



A common species in brooks and ditches. 



8. V. ORTHOCARPA Reinsch, 1887, p. 189, PI. VIII ; V. da- 



