96 University of Californiu Puhlicntions in Botany [yoh.% 



2. Calothrix robusta S. and G. 



Plate 6, fig. 22 



Filaments caespitose, attached at tlic base and erect, or attached 

 at the middle and both ends erect, somewhat tlexuoiis, cj'lindrical, 

 1-2 mm. long, 30— lO/t diam. ; trichomes nearlj' cj'lindrical throughout, 

 very abruptly pointed at the apex, rarelj' branching, not torulose, 

 16-20/A diam., bright blue-green, cells 2-3/a long, finely and uniformly 

 granular; sheaths hj'aline or slightly yellowish with age, lamellate, 

 7-8/i thick, closed at the apex when young ; heterocysts basal, much 

 compressed, 1-4/i, seriate. 



Forming a caespitose layer on rocks in small tide pools near high- 

 tide level. Cypress Point, Monterey County, California. 



Setchell and Gardner, in Gardner, New Pac. Coast Alg. Ill, 1918a, 

 p. 473, pi. 40, fig. 22. 



The material of this species shows but few heterocysts and these 

 are all basal, usually much compressed, and occasionally 2-4 seriate. 

 It has a thick, firm sheath, and this remains closed at the apex for some 

 time. The branching, so far as observed, is through a rupture either 

 on the side of the sheath, apparently caused by rapid growth of the 

 trichome in that part, the closed sheath at the apex not expanding 

 as rapidly as the trichome elongates, or more commonly by breaking 

 through the sheath at the base of procumbent filaments. 



Calothrix rohusta is to be placed near C. scopulorum from which 

 it diflPers decidedly in size, being, in fact, the largest species of the 

 genus, so far as thickness of filament goes, with the exception of C. 

 pilosa W'hich also it resembles to a certain extent. 



3. Calothrix scopulorum (Web. and Mohr) Ag. 



Filaments contorted, erect, up to 1 mm. high, lO-lS/x diam., mod- 

 erately thickened at the base, forming an expanded, caespitose, olive 

 green stratum; sheaths somewhat thick, hyaline, yellowish brown, or 

 colored in zones, usually lamellate, repeatedly ocreate; trichomes 

 olive green, 8-15ju, diam., prolonged into a long, hyaline hair; hetero- 

 cysts 1-3, basal, hormogonia numerous in a sheath, 4r-5 times as long 

 as the diameter. 



Growing in rock pools and on wood along high-tide level and above. 

 Puget Sound (Saunders, 1901, p. 399), and central and southern 

 California, 



