FOEESTS AND TREES OF NORTH AMERICA. 269 



J, the Texan, K, the Illinois, and L, the SasJcatcheivan regions^ 

 are characterized by prairies ; and the forests, which occur only near 

 their eastern borders and along the rivers, gradually decreasing 

 towards the west, are composed entirely of species characteristic of 

 the region eastward. No new ones occur, while a large number of 

 trees disappear at the commencement of prairies. M, the BacotaJi, 

 and N, the Camanche regions, are composed of these great treeless 

 and often arid plains which skirt the eastern slopes of the Rocky 

 mountains. Trees occur only in narrow belts along the rivers, and 

 for about three hundred miles east of the mountains most of the 

 streams are entirely woodless. 



These five regions are, however, supplied with numerous peculiar 

 plants and animals, mostly of quite distinct species from those of the 

 forest-clad regions eastward. They are so well marked, in these 

 respects, that, together, they may be considered as forming a natural 

 PROVINCE, which, from its most remarkable character of plains, is 

 called Campestrian. 



0, P, Q, may be named, from the Mexican States which partly com- 

 pose them, Tamaulipan, Choahuilan, and Chihuahimn regions ; but 

 too little is known of them to define their limits well. Their trees 

 are given in the list of those along the Mexican boundary, and these 

 are found almost exclusively along the Rio Grande, within the United 

 States. Only seven or eight species are found, in addition to the few 

 which extend from the Mississippi region and Florida. - - 8 

 R, the Arizonian region, though in great part treeless, furnishes 

 a large number of additional species, some of which are probably 

 more common in the adjoining Mexican States of Sonora and Lower 

 California, while others, chiefly among the San Francisco mountains, 

 seem to be nearly or quite peculiar. 



The former, thirteen in number, are included in the Mexican Boun- 

 dary list, while the fourteen characteristic and ten (?) peculiar are in 

 the catalogue of Western trees. - - - - - 37 



These numbers, except the total, must, however, be considered as far 

 from settled, as the surrounding regions are but little explored, and 

 in a region so poorly wooded, as most of it is, ten peculiar species 

 could scarcely be expected. It will be remarked also, that most of 

 these trees characteristic of the Mexican boundary are not over fifteen 

 or twenty feet high, and in many cases these are extreme heights. 

 Shrubs constituting the dense tliickets called chapparal take the place 

 of forests over great tracts. 



S, the Wasatch region, almost unexplored, is not known to have 

 any trees peculiar to it; but as the mountain summits are usually well 

 wooded, some may be hereafter found characteristic, if not peculiar. 1 

 T, the Padoucan, has apparently two peculiar pines, but its vege- 

 tation is scanty in forests, and but little explored. - - 2 

 U, the Utah region, being, as far as explored, almost woodless, it 

 is rather surprising to find that the only tree which is abundant on 

 some of its mountains is apparently almost peculiar to it — the Juni- 

 perns occidentalis. - - - - - - -1 



V, the Shoshonee region, though, like the last, almost woodless on 

 its plains^ has some well-wooded mountain ranges, on which a larch 



