io8 TUFTS COLLEGE STUDIES, VOL. II, No. 3 



enough to contain the spores, distinguishes this species from 

 others of the same general dimensions. 



2. S. PORTICALIS (Miiller) Cleve, 1868, p. 22, PI. V, figs. 

 8-13 ; Petit, 1880, p. 21, PI. V, figs. 8-12 ; P. B.-A., No. 365 ; 

 S. quinina Wolle, 1887, p. 213, PI. CXXXIV, figs. 14-17. 

 Filaments 30-48 fj. diam., cells 2-6 diam. long; chromatophore 

 single, quite broad, dentate, bright green, making 3-4 turns in 

 the cell ; fertile cells little or not at all swollen; spores ovoid 

 or subglobular, yellowish at maturity, i}4 diam. long; diam. 

 up to 42 p.. Mass., N. J., Pa., Iowa, Cal. 



Europe, Asia, So. America. 



A very common species, often forming extensive yellow-green 

 masses in quiet water ; very mucilaginous ; the broad, dentate 

 spiral, with many brilliant pyrenoids, is characteristic. 



Forma MINOR Collins, P. B.-A., No. 1263. Filaments about 

 42 p. diam. ; spores 30-35 p. diam. Conn. 



3. vS. JUERGENSII Kutzing, 1845, p. 222 ; Petit, 1880, p. 16, 

 PI. V, figs. 6 & 7 ; Wolle, 1887, p. 213, PI. CXLII, figs 3 & 4 ; 

 Rabenhorst, Algen, No. 1534. Filaments 24-26 p. diam. ; cells 

 2^-5 diam. long ; chromatophore single, slender, delicate green, 

 with pyrenoids much broader than the spiral ; fertile cells 

 slightly swollen, but no more than caused by the spores ; spores 

 30 p. diam., ellipsoid, twice as long as broad, golden color at 

 maturity. Cal. ; according to Wolle, generally distributed. 



Europe . 



Nearly allied to S. porticalis and 5". communis ; differing from 

 the former by smaller dimensions throughout; from the latter 

 by the different chromatophore, and by the shorter and stouter 

 spore. 



4. S. CATENAEFORMIS (Hass.) Kiitzing, 1849, p. 438; Petit, 

 1880, p. 17, PI. Ill, figs. 9-12; P. B.-A, No. 361. Filaments 

 24-27 p. diam., cells 2-5^ diam. long; chromatophore single, 

 quite broad, dentate, making 1-6 turns in the cell ; fruiting cell 

 swollen, up to 36 p. diam. ; spores ellipsoid with rounded ends, 

 yellowish at maturity, 2-2^2 times as long as broad, up to 30 /u. 

 diam. Mass., Cal. Europe. 



A quite variable species, but not difficult of recognition by the 

 combination of characters just given. 



5. S. VARIANS (Hass.) Kutzing, 1849, p. 439; Petit, 1880, 

 p. 19, PI. IV, figs. 1-8; Wolle, 1887, p. 212, PI. CXXXIV, 

 figs. 8-13 ; P. B.-A., Nos. 367, 962. Filaments 33-40 p. diam., 

 cells 2-3 diam. long; chromatophore single, quite broad, den- 



