968 The American Naturalist. [November 
The writer is greatly indebted to Professor R. C. Hills for 
his very full information in regard to the topography of the 
basin, and for assistance and advice in connection with the 
trip. 
PECULIAR ZONAL FORMATIONS OF THE 
GREAT PLAINS. 
By FREDERIC E. CLEMENTS. 
The traveller through the sand hills of Nebraska has often 
brought to his notice the striking way in which nature has 
marked, as though for all time, the fields and groves which 
once dotted the country. Such areas are always most conspic- 
uous, because of the strange contrast between their sharply 
marked dark green and the thin, brown vegetation of the sand 
hills. Frequently the waste is a flaming mass of the western 
sunflower, Helianthus petiolaris, in which case it is distinctly 
visible for several kilometers. In many localities, such wastes 
have existed for more than a score of years, and, instead of 
diminishing in any respect, become each year more and more 
accentuated. 
The elevated prairies and tablelands, which are so typical 
of the Great Plains before the latter rise into the foot hills of 
the Rocky Mountains, are characterized by a floral covering 
monotonous in the extreme. Trees and shrubs are entirely 
absent, and undershrubs are present only in peculiar alkaline 
areas, and in “bad lands.” The color-tone of the floral cover- 
ing is green only for one or two spring months: after the first. 
of June, it becomes a uniform straw color, stretching in all 
directions to the horizon. The two principal formations of the 
high plains of western Nebraska are the Stipa comata forma- 
tion, and the peppergrass-cactus formation. Rarely, the 
former is traversed by a sandy zone several kilometers wide 
and 20-30 kilometers long, characterized by the Artemisia fili- - 
folia formation. An individual of A. filifolia regarded alone 
is scarcely green, but the mass of individuals, by contrast with 
