1889.] The Vegetation of Hot Springs. 399 
of the upper basin, as well as the bright reds and yellows of 
Specimen Lake and the Orange Pool. 
Early in the study which was made of these springs, it was 
noticed that the color of the vegetation was, in a degree, de- 
pendent upon, or related to, the temperature of the water. 
This is well illustrated by the occurrence of Hypheothrix 
laviinosa, whose delicate filaments wave in the stream draining 
the Black Sand, where the following relation of color to tem- 
perature was observed : 
White— 185^ 
Flesh pink — 181 '^, becoming browner as the temperature 
falls. 
Pale yellow— 164^. 
Yellow green — 155''. 
P^merald green — 135^-140°. 
Dark green— 1 3o«. These colors merging, of course, into 
one another, but being very prominent at the temperature 
given. Other growths are : 
Orange — 125^. 
Red— no''. 
Cedar brown — 90*^. 
An examination of the growths forming the first series by 
Professor Farlow proves that the flesh-colored and white 
growth, occurring at i8o''-i85'', shows but traces of algae 
filaments in amorphous matter. At 164'' the structure was 
more decidedly filamentary and the color light yellow. The 
bright green forms at 155° were in a better condition for 
study, and the dark green filaments at 130° were in good con- 
dition. Hypheothrix laminosa probably attains its fullest and 
most perfect development in these waters between 130** and 
iSS^'Faiir. 
In those clear bowls of hot but never boiling water called 
^augs, the algai often form a leathery sheet lining the sides 
and bottom of the pools. Each sheet consists of a great 
number of thin, membranous layers aggregating one-fourth 
to one- half inch in thickness; the under layers are a rich 
tomato red, and the surface covered with a thin, incoherent 
