2 BULLETIN UNITED STATES GEOLOGTCAIi SURVEY. \YolYI. 



Whitney, to be a compreliensive appellation for the whole system of 

 mountains, from the most eastern Eocky Mountains to the Sierra I^N^evada 

 inclusive, and the continuation of the latter in the Cascade Mountains 

 of Oregon and British Columbia. The region which we are to treat 

 botanically might take the name of the Cordilleran Eegion of North 

 America. But it will, on several accounts, be better to adhere in this 

 essay to the designation used in our title. For, although the term ''Cor- 

 dilleras" would be the only appropriate one if we had the whole vast 

 mountain system in view, from Patagonia to the Arctic sea-coast, it is a 

 term which belongs j)rimarily and mainly to South America, and our 

 survey is to embrace only a few j)arallels of latitude, in fact just those 

 which contain the ranges which early took the name of the Rocky Mount- 

 ains, both at the north, where they were traversed by Lewis and Clarke 

 at the beginning of this century (1803-1806), and at the south, where 

 they were reached on the frontiers of New Mexico by Pike a year or two 

 later. 



With these Eocky Mountains proper, i. e. the eastern and dominating 

 ranges, as the central line of our field of view, the horizon should extend 

 eastward to where the gTadually subsiding plain becomes green with a 

 rich prairie vegetation, to be at length fringed with forest, and westward 

 to the base of the Sierra Nevada and the Cascades, the eastern verge of 

 the Pacific forest region. 



In a developed treatise, the physical geography and the climatic ele- 

 ments of the region would have to pass under review, and the multi- 

 farious and scattered botanical data would have to be collected, dis- 

 cussed, and tabulated. We cannot undertake an exhaustive task like 

 this, nor could we add much to what has already been done in various well- 

 considered and well-known government reports. The climatology and 

 the practical considerations deducible from it form the subject of Major 

 Powell's " Eeport on the Lands of the Arid Eegion of the United 

 States," the second edition of which was issued in 1879. In the " Gen- 

 eral Eeport " which forms the introduction to the botanical volume of 

 Clarence King's celebrated " Survey on the Fortieth Parallel " (and 

 which j)refaces that elaborate systematic treatise which was too mod- 

 estly styled a " Catalogue," and so has by some been cited as such), 

 Mr. Sereno Watson has thoroughly and ably discussed the elements of 

 the flora of the Great Basin, exemphfying it with lists and other details. 

 And for a district further south, Professor Eothrock, in his volume on 

 the Botany of Wheeler's Surveys, has within the last year published 

 his instructive notes on the characteristic features of the botany of Colo- 

 rado, New Mexico, and a part of Arizona. Professor Sargent has given 

 a useful sketch of the arboreal and frutescent vegetation of Nevada in 

 the American Journal of Science for June, 1879 ; and among Professor 

 Hayden's very important reports, that of Henry Gannett, " On the Ara- 

 ble and Pasture Lands of Colorado " (1875, reprinted in 1878), is note- 

 worthy. 



