ON THE CHARACTERISTICS OF THE NORTH AMERICAN FLORA. 567 



wanting, nntil the southern confines of the region are reached in Colorado 

 and New Mexico, and there they are few and small. In these southern 

 parts there is a lesser amount of forest, but a much greater diversity 

 of genera and species, of which the most notable are the pines of the 

 Mexican plateau type. 



The Rocky Mountains and the coast ranges on the Pacific side so 

 nearly approach in British America that their forests merge, and the 

 eastern types are gradually replaced by the more peculiar western. But 

 in the United States a broad, arid and treeless, and even truly desert, 

 region is interposed. This has its greatest breadth and is best known 

 where it is traversed by the Central Pacific Railroad. It is an immense 

 plain between the Rocky Mountains and the Sierra Nevada, largely a 

 basin with no outlet to the sea, covered with sage-brush (i.e., peculiar 

 species of artemisia) and other sub-saline vegetation, all of greyish hue ; 

 traversed, mostly north and south, by chains of mountains, which seem 

 to be more bare than the plains, but which hold in their recesses a con- 

 siderable amount of forest and of other vegetation, mostly of Rocky 

 Mountain types. 



Desolate and desert as this region appears, it is far from uninteresting 

 to the botanist ; but I must not stop to show how. Tet even the ardent 

 botanist feels a sense of relief and exultation when, as he reaches the 

 Sierra Nevada, he passes abruptly into perhaps the noblest coniferous 

 forest in the world, a forest which stretches along this range and its 

 northern continuation, and along the less elevated ranges which border 

 the Pacific coast, from the southern part of California to Alaska. 



So much has been said about this forest, about the two gigantic trees 

 which have made it famous, and its pines and fii\s which are hardly less 

 wonderful, and which in Oregon and British Columbia, descending into 

 the plains, yield far more timb.er to the acre than can be found anywhere 

 else, and I have myself discoursed upon the subject so largely on former 

 occasions, that I may cut short all discourse upon the Pacific coast flora 

 and the questions it brings up. 



I note only these points. Although this flora is richer than that of 

 the Atlantic in conifera? (having almost twice as many species), richer 

 indeed than any other except that of eastern Asia, it is very meagre in 

 deciduous trees. It has a fair number of oaks, indeed, and it has a 

 flowering dogwood, even more showy than that which brightens our 

 eastern woodlands in spring. But, altogether it possesses only one- 

 quarter of the number of species of deciduous trees that the Atlantic 

 forest has ; it is even much poorer than Europe in this respect. It is 

 destitute not only of the characteristic trees of the Atlantic side, such as 

 liriodendron, magnolia, asimina, nyssa, catalpa, sassafras, carya, and the 

 arboreous leguminosse (cercis excepted), but it also wants most of the 

 , genera which are common throughout all the other northern-temperate 

 floras, having no lindens, elms, mulberries, celtis, beech, chestnut, horn- 

 beam, and few and small ashes and maples. The shrubbery and herbaceous 

 vegetation, although rich and varied, is largely peculiar, especially at the 

 south. At the north we find 'a fair number of species identical with the 

 eastern ; but it is interesting to remark that this region, interposed 

 between the N.E. Asiatic and the N.E. American, and with coast ap- 

 proximate to the former, has few of those peculiar genera which, as I 

 have insisted, witness to a most remarkable connection between two floras 

 so widely sundered geographically. Some of these types, indeed, occur 



