MESA AND FOOTHILL VEGETATION 



45 



reaches its lower limit of altitudinal distribution at about 5,500 ft. and 

 hence is not abundant on the mesa. A few patches occur well toward 

 the upper end of the mesa. 



Wild Plum. Prunus americana Marsh. — A few wild plums are 

 found in both gulches, more occuring in Pole Canyon than in Cemetery 



Fig. 9. — Oregon Grape. Berberis repens Lindl. — This shrub is best developed on 

 the steep south slope at the upper part of the mesa. It is one of the first plants to bloom 

 in the early spring. Many of the early-blooming plants are found growing on the south 

 slopes where they receive the most heat of the sun. Since this plant flowers and develops 

 the fruit in the early spring, which in this area is usually the wettest part of the growing 

 season, it is not so dependent upon the amount of soil moisture during the rest of the 

 season, as are other later-blooming plants of the same habitat. For this reason its dis- 

 tribution on the steep south slopes does not explain its extreme xerophytic nature so 

 much as it does its relation to the time it blooms. 



Gulch. Several trees were found growing on north and south exposures 

 in dry soil. 



