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



3. Z. CYANOSPERMUM Cleve, 1868, p. 28, PL VIII, figs. 

 6-8. Vegetative cells about 20 ^ diam., 2-9 diam. long ; conju- 

 gation scalariform ; spores globose, 34-40 /x diam., in the short 

 tube; membrane bluish, smooth. Greenland. 



Northern Europe. 



4. Z. CHALYBEOSPERMUM Hausgirg, iSSSa, p. 257 ; P. B.-A., 

 No. 808. Vegetative cells 24-27 /u. diam., 1-3 diam. long, fertile 

 cells shorter ; membrane delicate ; conjugation scalariform ; 

 spores globose or subglobose, about 35 ^ diam. ; median mem- 

 brane bluish, smooth ; cells containing spore somewhat inflated. 

 Cal. Europe. 



5' Z. LEIOSPERMUM De Bary, 1858, p. 77, PL I, figs. 7-14; 

 Wolle, 1887, p. 222, PL CXLJII, figs. 1-3; Rabenhorst, Algen, 

 No. 638. Vegetative cells 20-22 // diam., as long or slightly 

 more ; conjugation scalariform or lateral ; fertile cells somewhat 

 swollen and shortened ; spores smooth, globose or broadly ovoid, 

 brownish, 23-30 p. diam., escaping from the cell before fully ripe. 

 Greenland, Mass. Europe. 



6. Z. INSIGNE (Hass.) Kiitzing, 1849, p. 444; 18553, p. 5, 

 PL XVII, fig. i ; De Bary, 1858, p. 78, PL VIII, figs. 14-16: 

 Wolle, 1887, p. 223, PL CXLJII, figs. 4-6; P. B.-A., No. 457. 

 Vegetative cells 26-30 /x diam., length equal to diam. or up to 2 

 diam. ; cylindrical or swollen on one side ; conjugation scalari- 

 form or lateral; spores 30-32 /j. diam., brownish, remaining en- 

 closed after maturity by the persistent cell wall. Mass., N. J., 

 Cal. Europe. 



Differs from the preceding species chiefly in dimensions, but 

 also by the different behavior of the ripe spore. 



7. Z. CRUCIATUM (Vauch.) Agardh, 1817, p. 102 ; Kiitzing, 

 i8 5 5a, p. 5, PL XVII, fig. 4; Wolle, 1887, p. 224, PL CXLIV, 

 figs, i and 2; P. B.-A., No. 758. Vegetative cells 35-54 ^ 

 diam., as long or somewhat longer; conjugation scalariform; 

 spores globose, brown, about 40 /* cliam., median membrane 

 finely punctate ; fertile cells not swollen. Mass., N. J. 



Europe, So. America . 



8. Z. STELLINUM (Miiller) Agarclh, 1824, p. 77 ; Wolle, 1887, 

 p. 223, PL CXLIII, figs. 7-17; P.B.A., No. 1172. Vegetative 

 cells 25-36 p diam., 1-3 diam. long; conjugation scalariform or 

 lateral; spores ovoid or oblong, 35-48X30-35)11, brown, median 

 membrane with rounded pits ; fertile cells hardly swollen. Fig. 

 7. Greenland, Mass., Conn., N. J. Europe. 



The dimensions are for the type ; a number of forms have 

 been described, in some of which the cell diameter does not 



