1^0.1.] GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 63 



lu the district we inhabit such interference is so recent that we have little diflSculty 

 in conceiving the conditions which here prevailed, a few generations ago, when the 

 "forest primeval" — described in the first lines of a familiar poom — covered essentially 

 the whole country, from the Gulf of Saint Lawrence and Canada to Florida and Texas, 

 from the Atlantic to beyond the Mississippi. This, our Atlantic forest, is one of the 

 largest and almost the richest of the temperate forests of the world. That is, it com- 

 prises a"greater diversity of species than any other, except one. 



In crossing the country from the Atlantic westward, we leave this forest behind ns 

 when we pass the western borders of those organized States which lie along the right 

 bank of the Mississippi. We exchange it for prairies and open jilains, wooded only 

 along the water-courses — plains which grow more and more bare and less green as we 

 proceed westward, with only some scattering Cottonwoods (i. e. Poplars) on the imme- 

 diate banks of the traversing rivers, which are themselves far between. 



In the Rocky Mountains we come again to forest, but only in narrow lines or patches ; 

 and if you travel by the Pacific Railroad you hardly come to any ; the eastern and the 

 interior desert plains meet along the comparatively low level of the divide which here 

 is so opportune for the railway ; but both north and south of this line the mountaina 

 themselves are fairly wooded. Beyond, through all the wide interior basin, and also 

 north and south of it, the numerous mountain chains seem to be as bare as the alka- 

 line plains they traverse, mostly north and south, and the plains bear nothing taller 

 than Sage-brush. But those who reach and climb these mountains find that their ra- 

 vines and higher recesses nourish no small amount of timber, though the trees them- 

 selves are mostly small and always low. 



When the western rim of this great basin is reached there is an abrupt change of 

 scene. This rim is formed of the Sierra Nevada. Even its eastern slopes are forest- 

 €lad in great measure ; while the western bear in some respects the noblest and most 

 remarkable forest of the world — remarkable even for the number of species of ever- 

 green trees occupying a comparatively narrow area, but especially for their wonder- 

 ful development in size and altitude. Whatever may be claimed for individual Eu- 

 •calyptus trees in certain sheltered ravines of the southern part of Australia, it is 

 probable that there is no forest to be compared for grandeur with that which stretches, 

 essentially unbroken, though often narrowed and nowhere very wide, from the south- 

 ern part of the Sierra Nevada in latitude 36° to Puget Sound beyond latitude 49°, and 

 not a little farther. 



Descending into the long valley of California, the forest changes, dwindles, and 

 mainly disappears. In the Pacific coast ranges it resumes its sway, with altered feat- 

 ures, some of them not less magnificent and of greater beauty. The Redwoods of the 

 -coast, for instance, are little less gigantic than the Big-trees of the Sierra Nevada, and 

 far handsomer, and a thousand times more numerous. And several species which are 

 merely or mainly shrubs in the drier Sierra become lordly trees in the moister air of 

 the northerly coast ranges. Through most of California these two Pacific forests are 

 separate ; in the northern part of that State they join and form one rich woodland 

 belt, skirting the Pacific, backed by the Cascade Mountains, and extending through 

 British Columbia into our Alaskan Territory. 



So we have two forest regions in North America — an Atlantic and a Pacific. They 

 may take these names, for they are dependent upon the oceaus which they respectively 

 border. Also we have an intermediate isolated region or isolated lines of forest, flanked 

 on both sides by bare and arid plains — plains which on the eastern side may partly bo 

 caWed jirairies — on the western, deserts. 



This mid-region mountain forest is intersected by a transverse belt of arid and alkft- 

 liuo plateau, or eastward of grassy plain — a hundred miles wide from north to south- 

 through which passes the Union Pacific Railroad. This divides the Rocky Mountain 

 forest into a southern and a northern portion. The southern is completely isolated. 

 The northern, in a cooler and less arid region, is larger, broader, more diffused. Trend- 

 ing westward, on and beyond the northern boundary of the United States, i t approaches, 



