64 DESMIDS OF THE UNITED STATE-. 



The only plant I have found to harmonize with this de- 

 scription, was collected by J. D. Smith in Florida. It agrees 

 very well except in length, being nearly equal to three 

 diameters. 



C. PABVULUM, Breb. Plate XXI, figs. 12, 13. 



Cells small, ovate elliptical, slightly constricted, apices 

 truncate, two to nearly three times as 1< 111,1: as wide ; margins 

 entire, or sometimes lightly crenulate; semi-cells short 

 conical, broadly truncate or sometimes with apex refuse : 

 cytioderm smooth or finely punctate. 

 Diameter 18-22 p. 



Florida, collected by J. D. Smith. 



C. AMERICANUM, Lagh. Plate XLIX, figs. 15, 16. 



Cells small, sinus rather obtuse and widening outwardly ; 

 semi-cells sub-circular, the center with seven larger granules 

 (six peripheral and one central) and twelve, more or less 

 distinct, around these; vertical view elliptic; lateral vi<-\\ 

 sub-circular. Membrane smooth excepting the central 

 granules. 



Diameter of cell 22 p. ; length 40 /<. ; thickness 18 //. ; 

 diameter isthmus 6 i*. 



Pond near Tewksbury, Massachusetts. 



C. GBANATUM, Breb. Plate LXI, fig. 13. Plate XVIII, figs. 



14, 15. 



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

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

 rounded angles, sides gradually converging; apex truncate : 

 variable in size. 



Diameter 20-32 /Y. ; isthmus about one-third the diameter. 



Frequent in quiet waters. Pennsylvania, New Jersey, Mas- 

 sachusetts, Florida and Minnesota. 



Plate LXI, fig. 13, is the typical form; the others, Plute 

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



(. WOLLEANUM. Lagh.. var. <;KAXULIFERUM. Lagh. Plate 

 XLIX. figs. 1, 2. Syn. C. pseudogranatum. Wolle. J)es. 

 U. S., p. 158. 



Cell rather large, one-fourth longer than wide; sinus 

 somewhat ampliated inwardly and outwardly: semi-cells 

 sub-semi-circular, base subreniforni, dorsum narrowly 

 rounded, angles rounded, margins finely erenulate-dentate; 



