61 
tain only plants suitaLle for growing in highly alkaline soil. 
Under. these conditions. we would expect to find an cxcessive.num- 
ber of new species and genera on these alkaline plains, but as.a 
matter of fact, we find very few. In all the ages which have 
passed since the glacial period, but two genera have been produced 
from Salicornia, which are Spirostachys and Sarcobatus, while the 
new species are very, very rare. But among the other plants, we 
new species and genera. It is in the hot regions of Arizona and 
northern New Mexico where the enormous differences in climate 
of the plains and mountains and the absence of great water 
courses, and the multitudes of scattered springs or water holes 
in my Schedule of Zonal Distribution, published 1898. I will only 
i important formations. Among the 
covers the old bed of the lake in the Bonneville area, and the Pyra- 
mid Lake formation, which extends from Walker Basin on the 
south to the Malheur on the north, occupying the old Lahontan 
B . * 
bed formation extending from Glenn's Ferry to St. Anthony. ies 
lower Snake river formation is also attractive, whic extends 
n ; 
lev formations. The Lower Colorado formation is a vast area 
and northward to Albuquerque, is w 
tion, which covers all those valleys and is characterized by ex- 
