560 Part IV. Chapter 3. 
SETCHELL') concludes after a study of the upper temperature limits of 
life that no living diatoms occur in strictly thermal waters and that the plants 
of hot springs belong to the Bacteriaceae and Cyanophyceae. The Cyanophy- 
ceae grow in water up to a temperature of 150°—ı158° F. (65°—68° C.); 
scantily at a temperature ranging between 168°—172° F. (75°—77° C.) while 
the Bacteriaceae endure highest temperatures and are abundant at 158°— 160° F. 
(70°—71° C.) and in considerable quantity at 180° F. (82° C.), and at (192° F.) 
89°C. Such plants live in silicious waters at a higher temperature than in 
calcareous waters, the limits being green algae 168°—172° F. (75°—77° C.) 
and chlorophylless plants at 192° F. (89° C.). 
As the water cools down, other forms of vegetable life appear, give var- 
iety to the colorations and give beauty to the borders of the hot pools and 
overflow channels leading from them. The sequence of temperatures and 
colors is somewhat as follows: White 160° F.—ı853° F.; yellow, 145° F.—ı60°F.; 
red, 130° F.; green 110° F.—ı30° F.; Sasha brön, 95°F. There are 
variations, however, in the sequence of these colors, owing to various envir- 
onmental conditions. Thus, in the Black Sand Basin and Specimen Lake, 
the range of color is somewhat this: White, yellow, flesh pink, bright pink, 
yellowish-green, emerald. The prevailing tints are yellow at ı85° F. (85° C.), 
green preponderating at 132°—ı50° F. (535°—65° C.) and prevailing green, 
104°—ı22° F. (40°—50° C.). = 
Studying the growths at several temperatures, we find Leptothrix laminosa 
growing at 135° F.—ı85° F.; Phormidium at 165° F.; Beggiatoa at 150° F. 
—ı65° F., and Sferulina at a lower temperature. The leathery felt about 
the edges of hot springs is due to species of Phormidium the smallest of 
which is found in water as hot as 166° F. (75° C.). Spirulina grows with Phor- 
midium and forms with it curious raised rims about such pools as Prismatic 
Spring. As the water grows cooler in the overflow streams species of Anabaena 4 
occur °). = 
Gloeocapsa, a blue- Br alga, is found growing on the sides of geyser cones, where steam Ei 
is escaping, forming ther delicate olive-green coloration. A kind of fibrous sinter is formed 
by the growth of the Helle A engsten gysophila, or the young form of Mastigonema therm- 
ale, the latter olive colored, and the sinter of the erater of the Excelsior Geyser?). A 
coarse sinter is due to a bright a species, Leptothrix, a finer variety to Leptothrix, (Hypheo eothrix} 
laminosa, ranging from white to flesh pink, yellow and red to green, as the water cools. Besides 
the above plants, which belong to the Bacteriaceae and the Cyanophyceae, ie in & ne “ 
= 
CHARLES R. BARNES, of the University of Wisconsin, to be Hypnum aduncum, var. grac cilescens- 
ı) Science, new ser. XVII: 934. June ı2, 1903. 
2) Davis, B. M.: Re a the hot Springs of the Yellowstone. Science. neW ser. 
VI: 145. 
3) WEED: loc. eit. 
