No.i.} ©RAT AND BOOKEB OH THE BOCK? MOUNTAIN FLORA, 17 



■ n or the vicinity of it, with a few exceptions. Prunt P tylva- 

 stoo, Populus baUamifera^ monilifera, and tremuloides, ma\ be >- ; i i < I to 

 come in from the northeast, and onlj the lasl extends 6m Into the dis- 

 Ihe Negundo and Jtmtpiritf Rrgtnfana, with FVaannw riruife, 

 belong to the Atlanta >n, and do do! penetrate far, unless we 



count the < )aliforniau Negundo as a derivative form. The connect ion * ith 

 Pacific forest species is closer; and for the reel they are mainrj Mexi- 

 can plateau types, of which the botanical district in question maybe 



ded as a northern extension. 



1\ Cltdractrristics of the herbaceous and shruhbi/ nqctation of the Rooky 



Mountain forert region. 



It was convenient and, indeed, needful to take the sylva of this region 



into one view, extending from British Columbia to New Mexico and Ari- 

 zona, and from the Rocky Mountains to the western verge ofthe Great 

 Basin. But in its northern part the distinction between woodland and 

 woodless country is less marked, and the general botany is comparatively 

 homogeneous throughout the whole Latitude, the Atlantic and Pacific for- 

 ►eing there in fact continent. Along the southern border, under 

 different conditions and with little and sparse forest, there is an 

 analogous mtermingling of the botanical elements, and the general 

 tation of these wide-apart extremes is very different. Our personal 

 : nations were math' on a middle and typical belt, on which the bot- 

 any of the central region under notice is most largely developed and 

 purely exhibited, and where Atlantic and Pacific botany are most widely 

 Bepai eographically. We shall do well, therefore, to restrict our 



Sketches t<> this central belt, comprising Colorado and the southern part 

 of Wyoming on the east. Utah in the center, and Nevada at the wot. 

 And when treating Of the vegetation which is fostered by the forest, 

 there is, in fact, only the eastern half of the district to consider. /. <■.. the 

 proper Rocky Mountains, the YVahsatch, and the I'intas. which connect 

 the-, twi 9. Par westward, throughout the Great Basin propel', 



there i> not forest tnougfa to impress any botanical character upon the 



humbler growth, although wherever there is moisture there is a veg 

 mm to correspond. 



A- ha- already been BUggested, the timber region is more extensive 



than the -rounds actually bearing forest The contraction ofthe latter 



limits is. no doubt, largely a consequence of forest fires 



through a long course of but we suppose that it is also due to 



an antecedent or accompanying cation of the 



<• which, however, had passed its Crisis before OUT ae- 



rith the region began, the turn be tifled to by the in 



ater in the Great ;e during tie 



. the plants w hich are 

 . lint t hose '■ hich extend 



