60 DESMII>s OF THE UNITED STATES. 



C. granatum, Brcb. Piatt- L, fig. 13. Plate XV, figs. 14, 15. 

 Cells one and one-half times as loug as broad ; constriction 

 narrow linear; semi-cells trapezoidal, with straight bases, 

 rounded angles, sides gradually converging ; apex truncate; 

 variable in size. 



Diameter 20-32 (i.\ isthmus about one-third the diameter. 

 Frequent in quiet waters. Pennsylvania, New Jersey, 

 Massachusetts, Florida, ami Minnesota. 



Plate L, fig. 13, is the typical form ; the others, Plate XV, 

 figs. 14, 15, are varieties, near Wille's variety elongatum. 



C. moniliforme, Ralfs. Plate XV, figs. 16, 17, 18, 19. 



Cell.- twice as long as wide; Bemi-cells spherical, united by 

 a narrow isthmus j tour semi-cells often in -eric-; 1 1 mem- 

 brane smooth. 



Diameter 16-24 ". 



Frequent in ponds, Pennsylvania, New Jersey, Massachu- 

 setts, Florida, etc. Fig. 18 represents a peculiarity noticed 

 now and then, that in multiplying by division, Introduction 

 p. 18 , the new daughter semi-cells are larger than those of 

 the mother cell ; if this i- aol always the case such are fre- 

 quently found. 



C. QLOBOSi m. Bulnh. Plate XLIX, figs. 14-17. 



( !ells small, lighl green, bicocciform, scarcely compressed, 



nearly one third longer than wide, \<r\ slightl} constricted, 

 miius acute; semi-cells circular exclusive of the confluent 

 bases, entire, cytioderm Bmooth or finely punctate. 

 Diameter 20-24 /'.; length 25-33 ,". 



Not infrequent in ponds intermingled with other form-. 

 Plate XV, fig. 20, represents a variety which stands be- 

 tween this -preie- and moniliforme. 

 Diameter about 20 ,". 

 Pennsylvania. New Jersey, Massachusetts. 



C. bioculatum, Breb. Plate XV, figs. 21, 22. 



< 'ells small, somewhat longer than broad ; constriction deep, 

 producing a gaping notch on each side. Semi-cell compressed, 

 oval, with convex base, short convex sides and rather flat 

 apex. Cytioderm smooth or finely punctate. Zygospore 

 globose, without spines. 



Diameter 1516 //.; length about 17 //. 



Rhode Island, .Massachusetts, Pennsylvania, New Jersey, etc. 



