OBSERVATIONS ON SOME WEST AMERICAN 
THERMAL ALG&. 
JOSEPHINE E. TILDEN. 
(WITH PLATES VIII—X) 
Iv is the purpose of this paper to present an annotated list, 
~ with drawings, of thermal algz, based on collections made in 
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‘several western localities during the past two years. 
Collection no. r was made by the writer in Yellowstone 
National Park during June and July of 1896. Specimens were 
preserved in formalin and a quantity of each kind was also dried. 
The natural color of the growths zz situ was compared with the 
Plates in Saccardo’s Chromotaxia, ed. 2, 1894. 
The hot waters of the Park are either calcareous, as at Mam- 
Pia ies Springs, or contain silica in solution, as at Norris, 
Lowes, Middle, and Upper Geyser Basins. Travertine results 
from the growth of alge in calcareous waters, and siliceous sin- 
ter in siliceous waters. 
Collection no. 2 was made by the writer from warm springs at 
Salt Lake City, Utah, in July 1897. 
Sul ania no. 3 was made by the writer from the Natural 
g phur Spring at Banff, Alberta, during the month of August 
1697, The warm springs of Banff are used for bathing pur- 
Bei They are situated on high ground and most of the over- 
i mors away by means of ditches, several feet deep, 
es ead down the stéep hillside. Here the water accumu- 
€s on a level Space and forms a shallow but quite extensive 
ie fag Some of the overflow escapes underground for a 
Out in ori ci ere ae ayaa halfway down the hill — 
sheets ot dase finally joins the stagnant water below. ese 
are still ¢ ater have naturally lost much of their heat, but they 
1898] ©pid and Support a — growth of Chara and other 
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