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



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

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

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

 tube; membrane bluish, smooth. Greenland. 



Northern Europe. 



4. Z. CHALYBEOSPERMUM Hansgirg, i888a, p. 257 ; P. B.-A., 

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

 cells shorter ; membrane delicate ; conjugation scalariform ; 

 spores globose or subglobose, about 35 /u, 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. Jtitrope. 



6. Z. INSIGNE (Hass.) Kiitzing, 1849, p. 444; iS55a, p. 5, 

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

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

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

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

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

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

 Cal. J 'I u rope. 



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, 

 18553, 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 p- 

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

 spores globose, brown, about 40 /u, diam., median membrane 

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



Europe, So. America. 



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

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

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

 lateral; spores ovoid or oblong, 35-48X30-35^, 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 



