BIOLOGICAL RELATIONS OF CERTAIN DESERT 
SHRUBS. , 
I. THE CREOSOTE BUSH (COVILLEA TRIDENTATA) IN ITS. 
RELATION TO WATER SUPPLY. . 
V. M. SPALDING. 
(WITH SEVEN FIGURES) 
THE general features of desert vegetation are well known and have 
been described in a voluminous literature. Certain striking pecu- 
liarities, such as the production of spines, development of tissue f 
These general and easily ascertained facts are by no means 
portant, and it is a decided advantage to botanical science that 
have been recorded in such numbers. A far more important | 
has become increasingly evident, namely that plants living to 
under present day desert conditions have each a history and | 
ter of its own, expressed in peculiarities of habits and physiolo 
activities, and evidence is not wanting that, with changing 
most complicated interrelations of organism and_ envirol 
rings the conviction that no general statement is an adequate & 
sion of the biological relations of any one of them, that each is 
to itself, and that its actual relations to the environment m 
determined for each species by critical study of its own struc 
and Physiological characteristics, one by one. It is from this 
of view that the present study has been undertaken, and for this 
Pose certain desert shrubs have been chosen—the creosote bush 
verde, and mesquite—all of which possess, each in its own Way; 
: [av 
