108 University of Californi.a Publications in Botany [Vol.8 



when dry, 3-5 mm. diam. ; filaments crowded; sheaths narrow, firm, 

 inconspicuous below, spreading and slightly colored above; trichoraes 

 2.5-5/A diam., blue-green, prolonged into a long, delicate, hyaline 

 thread above; cells of equal diameter below, shorter above. 



Growing on rocks in the upper littoral belt. Ranging from central 

 to southern California. 



Bornet and Flahault, Rev. II, 1886, p. 355; Collins, Holden and 

 Setchell, Phyc. Bor.-Amer. (Exsicc), no. 1561. Bivularia hemii- 

 sphacrica Kuetzing, Actien, 1836 (cf. note under Bibliography). 



Rivularia atra var. confluens (Kuetz.) Bornet 



Thallus a flat confluent mass, 2-5 cm. across, adhering firmly to 

 rock, deep blue-green, glossy; filaments closely adhering; sheaths 

 hyaline when young, colored in zones with age ; trichomes 5-7 ju, diam., 

 170/x long; heterocysts 7-10/a diam., nearly spherical, very numerous. 



Growing on dripping rocks at high-tide level and above. Carmel 

 Bay, Monterey County, California. 



Bornet, Alg. de Schousb., 1892, p. 189 (p. 29, Repr.) ; Collins, 

 Holden and Setchell, Phyc. Bor.-Amer. (Exsicc), no. 2107. Euactis 

 confluens Kuetzing, Sp. Alg., 1849a, p. 341, Tab. phyc, vol. 2, 1850- 

 52, p. 24, pi. 77, fig. 1. 



3. Rivularia nitida Ag. 



Thallus variable in shape, spherical, and sometimes hollow, or 

 expanded and plicate corrugate ; up to 3 cm. diam. ; olive green ; fila- 

 ments crowded ; sheath narrow, close fitting, indistinct below, slightly 

 expanding upward, hyaline or yellowish brown ; trichomes 2-5/x diam., 

 olive green, prolonged into a very narrow long hair; cells 3^ times 

 longer than the diameter below, but the upper cells shorter than the 

 lower. 



Growing on mud near high-water mark. St. Michael, Alaska. 



Agardh, Dispositio Alg. Suec, 1812, p. 44; Bornet and Flahault, 

 Rev. II, 1886, p. 357 ; Setchell and Gardner, Alg. N.W. Amer., 1903, 

 p. 198. 



The specimen from Alaska credited by us to this species seems to 

 agree in microscopic details with the descriptions and in habit very 

 well with figure 1, on plate 2518 of the Flora Danica (1849). 



