10 



FOREST TREES OF NORTH AMERICA. 



the Pacific region are mingled with pines, a juniper, an arbutus, and various other species peculiar to the Mexican 

 plateau. Extensive forests of a cypress of Mexican origin also characterize this mountain vegetation. The 

 bottoms of the canons are lined with a dense growth of cotton wood, hackberry, a noble sycamore, an ash, a 

 cherry, and other deciduous trees. The high foot-hills and wcsas are covered with open groves of various oaks 

 peculiar to the Mexican-Pacific region, here reaching, within the United States at least, their greatest development. 



Such are some of the prominent forest features of North America; a dense forest, largely composed, except 

 at the north, of a great variety of broad-leaved species, and extending from the Atlantic sea-board in one nearly 

 unbroken -sheet until checked by insufficient moisture from further western development the forest of the Atlantic 

 region ; a forest of conifers, occupying the ranges of the great Cordilleran mountain system, unsurpassed in 

 density in the humid climate of the coast, open and stunted in the arid interior the forest of the Pacific region. 



A more detailed examination of the distribution of North American arborescent genera and species will serve 

 to illustrate the wealth of the forests of the Atlantic and the comparative poverty of those of the Pacific region. 

 It will show, too, more clearly how widely the forests of these two great regions differ in composition. 



DISTRIBUTION OF GENERA. 



The forests of North America contain arborescent representatives of 158 genera; 142 genera occur in the 

 Atlantic and 59 genera in the Pacific region. Of the Atlantic genera, 48 are not represented in the United States 

 outside the semi-tropical region of Florida. 



The following table illustrates the distribution of these genera; the genera of semi-tropical Florida are 

 designated by a *. 



