398 The American Naturalist. [May, 
Farlow's hands will yield important information concerning 
the morphology of the species. 
In a study of the hot springs and the geyser phenomena of 
the Yellowstone National Park, carried on in connection with 
my geological work in that region, I was surprised to find an 
abundant algous vegetation in the hot springs even at very 
high temperatures. It has been found by an examination of 
the hot springs of the region, of which nearly 3,500 have been 
individually and carefully noted, that algae are almost univer- 
sally present either in the springs themselves or in the streams 
flowing from them. The only exceptions to this are the mud 
bowls, and even here algae are often found on the borders 
where kept moist by steam. This widespread occurrence im- 
plies that algae can exist under a very great diversity of con- 
ditions. The springs examined differ greatly in the chemical 
composition of their waters, and include carbonated, calcare- 
ous and siliceous alkaline waters, and also those acid with 
hydrochloric or with sulphuric acids. The alga also occur 
under equally diverse thermometric and hygrometric condi- 
tions ; they have been found at all temperatures up to 185 
Fahr., though from 160'' to 185^ they have thus far been ob- 
served only in running streams. 
It is difficult to give a general description of the vegetable 
life of hot springs which shall be brief, and yet convey any 
idea of the beauty and the varied forms of these growths. 
The vegetation of the acid waters (with free HCl or H,SO.) is 
seldom a conspicuous feature of the springs. But in the alka- 
line waters that characterize the geyser basins, and in the 
carbonated, calcareous waters of the mammoth hot springs, 
the case is otherwise, and the red and yellow tints of the algae 
combine with the weird whiteness of the sinter and the varied 
blue and green of the hot water to form a scene that is, without 
doubt, one of the most beautiful as well as one of the strangest 
sights in the world. Those who have been so fortunate as to 
, have seen the hot water fountains of the Yellowstone will be 
sure to remember the delicate and charming tints that char- 
acterize the basins about Old Faithful and many other geysers 
