1898] SOME WEST AMERICAN THERMAL ALGH# 95 
diameter, bright blue-green, granular, distinctly articulated or 
rarely with dissepiments not visible, sometimes moniliform, in 
older plants paler aeruginous, much narrower, with shorter 
articulations, not plainly visible, with apex tapering to a hair- 
point; articulations equal in length to diameter, but often, par- 
ticularly in younger plants, twice the diameter in length; 
heterocysts 1-2 seriate, basal or intercalary, very variable in 
size and shape. 
(a) Overflow of channel of geyser. Temperature 49-54.5° C. 
Spasmodic Geyser, Upper Geyser Basin, Yellowstone National 
Park. W. H.W. 1897. 
(0) Forming cedar-colored fur on overflow channel of 
geyser. Old Faithful Geyser, Upper Geyser Basin, Yellowstone 
National Park. W. H.W. 1807. 
(c) With other alge in rivulets. Temperature 49-50° C. 
Fountain Hotel Geyser Basin, Yellowstone National Park. J. 
E.T. 29 Je 1896. 
(d) Very common in colder portions of overflows. Varying 
in color from wmbrinus to castaneus and fuligineus. Growing in 
small islands or forming smooth surfaces. Temperature 34° C. 
Emerald Pool, Upper Geyser Basin, Yellowstone National 
fatk, 1. &. T. 3 Jl 1896. 
ae Weed has frequently mentioned this plant, but under 
ames. He describes an algal sinter which, ‘‘forming in 
the overflow channels of many of the geysers of the Upper 
Basin, is finel 
littl This sinter is formed by the growth of the 
ie alge, Calothrix gypsophila Kg., or the young form, 
sonema thermale, the latter olive-colored.”* Again, ‘the 
ce of algal sinter forming the deposits about the 
€yser Basins 
th 
Ley + 
ormat : os ; : ; 
U.S. Geol, A of travertine and siliceous sinter by the vegetation of hot springs. 
urv. oth Ann. Rep., 665. 1889 
. 
