a 
It is the onl 
1898] SOME WEST AMERICAN THERMAL ALGH 99 
2.5-3.2u in length; dissepiments marked by granules; apical 
cell acutely conical; no calyptra. 
(2) In overflow water of spring where the old formation 
makes a hard, billowy or terraced incline, the alge extend down 
the incline for a distance of twenty feet, forming wide ribbons 
of green alternating with bands of pink, yellow, white, and a 
darker green. Temperature of spring 91°C. The algal growth 
occurs at a temperature of 51-55°C. Ribbon Spring, Norris 
Geyser Basin, Yellowstone National Park. J. E. T. 27 Je 1896. 
(6) In small shallow spring, expanding at top in leaf-like 
masses, or tapering from bulbous head to a small tubular base. 
Temperature 55°C. Valley of Nez Perces creek, Lower Geyser 
Basin, Yellowstone National Park. J. E. T. 28 Je 1896. 
(c).In grassy rivulet. Temperature 30°C. Mountain hot 
springs, Lower Geyser Basin, Yellowstone National Park. 4 
E. T. 28 Je 1896. 
(¢7) Around edges of springs. Forming brown and green 
layers which turn gray or blackish out of the water. Tempera- 
ture 63°C. Prismatic Lake, Middle Geyser Basin, Yellow- 
stone National Park. J. E. T. 2 Jl 1806. 
(e) Forming plumy strings, white or light yellowish in color. 
Temperature 75.5°C. Solitary Spring, Upper Geyser Basin, 
Yellowstone National Park. J. E. T. 3 Jl 1896. 
(f) Forming whitish, scurfy, hardened, rather brittle scum 
on surface of still pool into which overflow runs. Temperature 
41°C. Mammoth Hot Springs, Yellowstone National Park. 
JE. T. 8 Jl 1896. 
as this species to be by far the most widespread and 
a eat. any alga in the hot waters of the park. Its habit 
1S extremely varied, so that it is not easily recognized. 
know, is {, if species, except Spirulina major, that, so far as J 
ee. ound in both calcareous and siliceous waters in. this 
P : + 
HORMIDIUM LAMINOSUM (Ag.) Gomont, forma Weedil, n. . 
(PL IX, fig. 16.) 
