92 ILLINOIS ACADEMY OF SCIENCE 



the aggregate between the elevations of the Utah and the Wyo- 

 ming stations, which are devoted to successful agriculture and 

 in the three states in which these stations are located there are 

 more than a million acres, so the subject becomes of some im- 

 portance locally. 



It is generally known that the environmental factors vary 

 with change in altitude, but the extent of the change is not 

 so well understood, empirically an increase of a thousand 

 feet in altitude is equivalent to a shift of 300 miles from the 

 equator, so it would be possible upon land elevated at the 

 equator to have all the zones with corresponding flora and 

 fauna. Actually, however, conditions are not the same as, 

 but similar to, the zonal. 



The higher altitudes are marked by the following peculiar 

 climatic conditions, which are not necessarily peculiar to 

 changes in latitude : 



A marked daily range of temperature which increases with 

 altitude. 



Mean daily temperature decreasing with altitude. 



Comparatively high solar radiation. 



Prevailing high winds, increasing with altitude. 



Comparative high evaporation because of the lowered air 

 pressure. 



As we pass to the higher altitudes the following changes are 

 noted in vegetation : 



The less hardy varieties and species give place to the more 

 hardy. 



The average height of the plants of any species decreases. 



The proportion of plant above ground to that below de- 

 creases. 



The proportion of seed to stock and leaves tends in general 

 to increase. 



The period between germination and seeding decreases. 

 Decreased acre yields. 



