Bohemia. Later, Cohn, in 1862, showed that the alire of tliese 

 springs deposited travertine. Sir WilHam Hooker, in 1809, found 

 CONFERVACE^ at the borders of many of the hpt springs there. Con- 

 ferva limosa, C. flavescens, C. rivularis were abundant in the water. 

 Baring Gould, who visited the Icelandic geyser region in 1864, 

 found in the overflow channels of the spring, Tunguhver, a species 

 of the genus Hypheothrix, common in hot waters all over the world. 

 In New Zealand, the presence of algae in hot springs has been deter- 

 mined. In the hot springs of the Azores, Mr, Moseley found algae 

 forming a pale yellowish-green layer an inch and a half thick. The 

 temperature of the water was 176" F. to 194° F. A thick, brilliant 

 green growth, consisting of Chroococais was found at the edge of a 

 shallow pool of hot water, where the temperature was between 

 149° F. and 156° F. 



In the hot springs of the Yellowstone no plant life has been found 

 at a temperature exceeding 185° F,, some degrees below the boil- 

 ing point of water, which, at the altitude of the park (7,000-8,500 

 feet) is 198° F. The most luxuriant growth of algae is found in 

 water which has cooled down to a temperature of 104° F. to 122° F. 

 In water of a temperature ranging from 100° F. to 125° F., we 

 have the greatest display of color, because many green algae can 

 live in nater of that degree of heat. In the hottest waters (185^ F.) 

 only white filamentous bacteria are found, which gradually become 

 of a sulphur-yellow color at 175° F. This yellow growth is due to 

 a species of Beggiatoa^ a plant which may be classed with the Bac- 

 TERiACE/E, and which, during life, deposits sulphur granules. 



As the water cools down, other forms of vegetable life appear, 

 give variety to the colorations and give beauty to the borders 

 of the hot pools and overflow channels leading from them. The 

 sequence of temperatures and of colors is somewhat as follows: 

 white, 160° F.-i85° F.; yellow, 145° F.-i6o° F.; red, 130° F; green, 

 110° F.-i30° F,; green-orange-brown, 95° F. There are varia- 

 tions, however, in the sequence of these colors, owing to various 

 environmental conditions. Thus, in the Black Sand Basin and 

 Specimen Lake, the range of color is somewhat this: White, yel- 

 low, flesh pink, bright pink, yellowish-green, emerald. 



Studying the growths at the several temperatures, we find Lcpto- 

 thrix lammosa growing at 135° F -185'^ F.; Phonnuiiuvi at 165° F. ; 

 Beggiatoa at i 50'^ F.-i65° F., and Spiru 'ni at a lovver temper, uuic 



