MESA AND FOOTHILL VEGETATION 



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but it must be remembered that in this area differences of altitude are of 

 little consequence in determining plant distribution. The contour lines 



Fig. 3. — Topographic Map of Horse and Long Mesas.— Contour interval 50 feet. 

 The numbers on the contour lines indicate feet above sea-level. The area shown is about 

 500 acres. The map shows clearly the even top of the mesas sloping gently toward the 

 northeast. The limit of this even top is indicated by the broken line. Here the steep 

 sides of the mesa begin. The sides are cut by numerous small ravines. The broad 

 amphitheater-like ravines are indicated. Three of the more important of these are marked 

 by X on the map. 



on the map are not of so much importance in marking altitudes, as in 

 showing the direction and steepness of slope. 1 



■ The altitude seems to be of importance in the distribution of a few shrubs. See Mr. Robbins' article 

 on "Deciduous Trees and Shrubs." 



