ii4 TUFTS COLLEGE STUDIES, VOL. II, No. 3 



ments than that noted above ; his plant seems intermediate be- 

 tween S. flavescens and 5". gracilis. 



21. S. GRACILIS (Hass.) Kiitzing, 1849, p. 438 ; Petit, 1880, 

 p. 15, PI. Ill, figs. 7 and 8 ; Wolle, 1887, p. 211, PI. CXXXIV, 

 fi s - 5~7> P- B.-A., No. 1418. Filaments 1 8-2 1 /A diam.; cells 

 3-5 diam. long ; chroniatophore single, quite broad, rich green, 

 making ^-3 turns in the cell ; fertile cells swollen only on the 

 conjugating side, the other remaining straight ; spores ovoid, 

 yellowish at maturity, diam. about 30 /j., length about double. 

 Mass., Michigan. Europe. 



22. S. LUTETIANA Petit, 1879, p. 97, PI. VI; 1880, p. 21, 

 PI. IV, figs. 9-13; Wolle, 1887, p. 214, PL CXXXV, figs. 7 

 and 8 ; P. B.-A., No. 1065. Filaments 30-36 ^ diam., cells 3-7 

 diam. long ; chroniatophore single, broad, dentate, dark green, 

 making 3-7 turns in the cell ; fertile cells sometimes swollen, 

 sometimes cylindrical ; spores polymorphous, globular, ellipsoid, 

 oblong, cylindric-ellipsoid, pyriform or reniform ; yellowish at 

 maturity, 2-4 diam. long; diam. 30-43^. Mass., Washington, 

 Florida ? Europe. 



The most distinctive character of this species is found in the 

 polymorphous spores. Wolle's description of the Florida plant 

 leaves considerable doubt as to its identity with Petit's species. 



23. S. TERXATA Ripart, 1876, p. 162 ; Petit, 1880, p. 26, 

 PI. VIII, figs. 4-7 ; Tilden, American Algae, No. 159, as 

 6". neglecta. Filaments 50-65 /j. diam., cells 1^2-2 diam. long, 

 somewhat swollen at the middle ; chromatophores three, narrow, 

 with apparent middle line uniting the pyrenoids, making 1)2-2 

 turns in the cell ; fertile cells swollen and shortened, often 

 shorter than the diam., so that the spores are turned at right 

 angles to their usual position ; spores ovoid, 45-66 //. diam., 1-1^2 

 diam. long. 111., Colorado. Europe. 



This species is nearly allied to S. neglecta, but the cells are 

 shorter, especially the fertile cells, and the spores are often so 

 closely set that the}- are side by side, their longer axes at right 

 angles to the direction of the filament. 



24. S. FLUVIATILIS Hilse in Rabenhorst, Algen, No. 1476 ; 

 Petit, 1880, p. 27, PI. V, fig. 13; Wolle, 1887, p. 216, PI. 

 CXXXVI, figs. 1-3; P. B.-A., Nos. 1217, 1417. Filaments 

 36 ju diam., cells 5-6 diam. long; chromatophores 4, slender, 

 very pale green, making 1^2-2^2 turns in the cell : fertile cells 

 swollen and shortened; spores ovoid, about 50 So /x. Mass., 

 Pa. Europe. 



No spores have been reported from the European localities, 



