1919] Setchell-Gardner : Myxophyceae 107 



man Exped., 1901, p. 399 ; Bornet and Flahanlt, Rev. II, 1886, p. 352 ; 

 Collins, liolden and Setchell, Phyc. Bor.-Amer. (Exsicc), no. 358; 

 Tilden, Amer. Alg. (Exsicc), no. 570. Rivularla nitid€, Tilden, Amer. 

 Alg. (Exsicc. ) , no. 571 (not of Agardh ) . Rivularia atra var. coadunato 

 (Sommerf.) Bornet, Les Nost. Het. Syst. Alg., 1889, p. 6. Linckia 

 atra var. coadunata Sommerfelt, Suppl. Fl. Lapp., 1826, p. 201. Rivu- 

 laria coadunata Foslie, Contrib. Knowl. Mar. Alg. Norway II, 1891, 

 p. 56 (p. 21, Repr.) ; Forti, in De-Toni, Syll. Alg., vol. 5, 1907, p. 667. 



This species is not uncommon and is more often growing in strictly 

 fresh water than in salt water. It grows on rocks and on hard soil, 

 among mosses, etc., where fresh water from springs or streams trickles 

 over it, but frequently the laj^ers extend down into the salt water 

 where it seems to thrive. 



It seems best to retain the name of Rivulari<i Biasolettiana as 

 chosen by Bornet and Flahault (loc. cit.) as against R. coadunata 

 (Sommerfelt) Foslie, and an additional reason exists for this choice, 

 since the name coadunata, as used by Sommerfelt, was simply varietal 

 and was raised to specific rank subsequent to the proposal of Biasolet- 

 tiana as specific (cf. Regl. Intern, de la Nom. Bot., Vienna, 1906, 

 Art. 49). 



2. Rivularia atra Roth 



Thallus spherical, solitary or confluent, blackish green, up to 4 mm. 

 diam. ; filaments thickly compacted, not separating readily under 

 pressure ; sheaths thin, scarcely distinct, ampliate above, hyaline or 

 3^ellow ; trichomes 2.5-5/a thick, verdigris green, produced above into 

 a slender hair ; lower cells scarcely longer than broad, upper shorter. 



On various solid living and non-living substrata. California. 

 Dr. C. L. Anderson (fide. Bornet and Flahault, loc. cit., p. 355). 



Roth, Cat. Bot., vol. 3, 1806, p. 340 ; Bornet and Flahault, Rev. II, 

 1886, p. 353. 



This species is given by Bornet and Flahault as occurring on the 

 coast of California. The specimens we have seen belong to one or 

 another of the two following varieties. 



Rivularia atra var. hemisphaerica (Kuetz.) B. and F. 



Plate 8, figs. 1, 2 



Thallus hemispherical, firm, solitary, or occasionally slightly con- 

 fluent by close proximity to others, of very dark green color, black 



