194 TUFTS COLLEGE STUDIES, VOL. II, No. 3 



6. M. FLOCCOSA (Vauch.) Thuret, 1850, p. 222, PI. XVII, 

 figs. 4-7; Hazen, 1902, p. 173, PL XXIV, figs. 1-4; P. B.-A., 

 No. 864. Conferva floccosa Wolle, 1887, p. 140, PI. CXX, figs. 

 21-25. Filaments bright or yellowish green, cylindrical or very 

 nearly so, 14-17 (rarely 18) //.diam.; cells 1-2^2 diam. long, with 

 thin walls ; chromatophore pale green, often perforated or in net 

 form ; akinetes 18-22 /u. diam., sphaeroidal, cuboidal or subcylin- 

 drical. Fig. 68. Mass, to N. J., Vancouver I. Europe. 



A very common spring plant, forming loose floccose masses in 

 slow streams and quiet waters. 



7. M. WILLEANA Lagerheim in De Toni, 1889, p. 228; 

 Hazen, 1902, p. 17-5, Pi. XXIV, figs. 5-7; P. B.-A., Nos. 619, 

 1326. Filaments cylindrical, light green, 11-14^, diam.; cells 

 ^2-1^2 (rarely 2) diam. long, wall thin ; chromatophore vari- 

 able, but usually denser than in M. floccosa ; akinetes 14-16.5 /u, 

 diam., spherical to subcylindrical. Mass, to N. J., Alaska, Cal. 



Europe. 



Occurring in the same localities as M. floccosa, and much re- 

 sembling the latter, but with somewhat smaller filaments and 

 decidedly smaller akinetes. 



8. M. STAGNORUM (Kiitz.) L,agerheim, 1887 a, p. 417; 

 Hazen, 1902, p. 176, PI. XXIV, figs. 12-13 ; P- B.-A., No. 618. 

 Filaments cylindrical, 7.5-9.5 (usually 8) /x diam., cells 1-3 diam. 

 long, wall thin ; chromatophore not dense, and often occupying 

 only the middle part of the cell. Greenland, Maine to N. J. 



Europe, So. America. 



A common species of early spring, but occurring also in 

 summer and autumn, often in company with other species of 

 Microspora or Ulothrix. 



9. M. TUMIDULA Hazen, 1902, p. 177, PI. XXIV, figs. S-n ; 

 P. B.-A., Nos. 1025, 1277. Filaments with distinct constrictions 

 at the dissepiments, 6.7-9.5 (usually 7.5) p. diam. ; cells 1-2 

 diam. long ; chromatophore rather dense, nearly or quite cover- 

 ing the cell wall ; akinetes S-n ^ diam., spherical or flattened. 

 Greenland, Mass., to N. J., also at Banff, Canada. 



Forming dull green skeins or floccose masses in brooks and 

 pools ; much like I\l. stagnorum, from which it is distinguished 

 by the distinctly contracted dissepiments and the more uniform 

 chromatophore. 



10. M. OUADRATA Hazen, 1902, p. 178, PI. XXIV, figs. 14 

 and 15; P. B.-A., No. 1276. Filaments light green, perfectly 

 cylindrical, 5.5-7 /^ diam. ; cells >^-i diam. long, with very thin 



