< I 8MARITJM. 63 



I have recognized two tonus of this plant ; the one longer 

 than the other ; the longer slightly retuse, which is the typi- 

 cal form ; the other not retuse. and not bo loner. The figures 

 represent the variety. 



Sometimes found in considerable numbers in <:elutinous 

 gatherings on dripping rocks and in small pools. 



C. VARIOLATUM, Lund. Plate X V I . figs. 3, 4. 



Small elliptical, twice as long as wide, constriction deep, 

 narrow, limar; semi-cells, base straight, sides rising at right 

 angle-, then curving gradually and producing an almost circular 

 apex, sometimes slightly retuse; end view broadly elliptical ; 

 side viewobovate. Cytioderm more or less punctate ; isthmus 

 one-third of the whole diameter. Chlorophyl nucleus single. 



Diameter 15-1 7 ". 



Ponds, southern New Jersey, rlammonton, etc. 



C. oontractum. Kirch. Plate XVI, fie. 1. Plate L, fig. 24. 



('ell.- one and one-halt' thm- as long a- wide; sinus pro- 

 duced l>y the constriction, deep and narrow, widening out- 

 wardly fr the base. Semi-cells oval, with convex base and 



convex apex, containing each one chlorophyl nucleus; cytio- 

 derm distinctly punctate. 



Diameter L' \ a. 



Denmark, and other pond-. New Jersey. 



C. 8EXangulare, Lund. Plate XVI, figs. 8,9. Plate XLIX, 

 fig. 13. 

 One-fifth part longer than wide; constriction deep; -inns 

 linear within and widening outwardly. Semi-cell- more or 

 less hexagonal-elliptic ; end- truncate, -ides obtusely rounded ; 

 end view elliptical; side view circular. Cytioderm finely 

 punctate. 



Diameter 25 \'l u. 



Occurs frequently in ponds, Pennsylvania, New Jersey. 

 The hexagonal feature of the semi-cells is not always as dis- 

 tinct as described ; in the figures 8 and 9 it was inadvertently 

 omitted altogether, nevertheless, they represent a common 

 form of the species. 



