THE GREEN ALGAE OF NORTH AMERICA 313 



3. Filaments laterally united. 4. 



3. Filaments free. i. C. soluta. 



4. Disk somewhat irregular in outline ; cells usually 25 /j. -wide or 



more. 4. C. scutata. 



4. Disk regularly orbicular; cells seldom over 15 M diam. 



5. C. orbicularis. 



5. Epiphytic. 2. C. irregularis. 



5. Endophytic. 3. C. Nitellarum. 



6. Forming uniformly rounded masses ; filaments radiating from the 



center. 6. C. pulvinata, 



6. Masses irregular ; filaments with no common center. 



7. C. divergens. 



1. C. SOLUTA (Breb.) Pringsheim, 1860, p. 6, PI. I, figs. 2 

 and 3 ; PL IV, figs, i and 2 ; Wolle, 1887, p. 64, PI. LXXII, 

 figs. 1-7. Filaments branching, radiating from a common 

 center, prostrate, not laterally united ; vegetative cells 12-25 /* 

 diam., 2-3 diam. long; oogonia at first lageniform, then glo- 

 bose, corticated, up to 200 //. diam., including cortex; oospore 

 100-150 /A diam. ; antheridia flask-shaped, about 17 ^ diam. 

 Mass.,- N. J. Europe. 



2. C. IRREGULARIS Priiigsheim, 1860, p. n, PL I, fig. 6; 

 PL VI, figs. 3-9; Wolle, 1887, p. 65, PL LXXII, figs. 15-16. 

 Filaments prostrate or decumbent, free or more or less united, 

 quite irregular, not forming a disk ; cells quadrangular or 

 polygonal, up to 25 //. diam., 1-172 diam. long; oogonia ovoid, 

 either quite naked or somewhat corticated above, about 120X65 

 ju, ; antheridia? Pa., N. J. Europe. 



The only species with regular outline to the frond, but fila- 

 ments not laterally united. 



3. C. NiTELLARUM Jost, 1895, p. 434, PL XXXIV; C. ir- 

 regularis P. B.-A., No. 974, not Pringsheim. Fronds endophytic 

 in cell wall of Nitdla or Chara ; filaments simple or branched, 

 more or less united to form a membranous expansion ; cells very 

 irregular in outline, much flattened; no erect branches; setae 

 penetrating the wall of the host and projecting externally ; 

 oogonia spherical or flattened, more or less corticated above ; 

 antheridia small cells cut off from the vegetative cells, usually a 

 number together. Mass., N. Y., Neb., Mexico. 



Europe, So. America. 



Much resembling C. irregularis in general characters, except 

 as modified by the peculiar habitat. Probably all reports of C. 

 irregularis on Chara or Nitella refer to this species ; it w r as dis- 

 tributed under the name of C. irregularis in P. B.-A., No. 974. 



