ITo.U GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 15 



range, as it extends from the Gulf of Saint Lawrence to that of Mexico, 

 and northwestward into British Columbia, wliile southwestward it 

 reaches Utah. In the Northern Rocky Mountains it is associated with 

 «7. saMna; in the Southern with the following species. Invaluable as 

 its wood is, the tree is not large or abundant enough in the region under 

 consideration to be of much account. 



Juniperus occidentalis and J. Californica, the Western Eed Cedars, 

 have also a great range, a dubious variety of the former (too near a 

 Mexican species) being the Cedar of Western Texas. The two in their 

 various forms are very striking and characteristic trees of the dry inte- 

 rior region. Like the eastern species, they are sometimes mere shrubs, 

 sometimes large but low trees. 



Juniperus pachypMoea, named for its very thick bark, which is likened 

 to that of a Pine or of White Oak, takes the place of these species in 

 Western New Mexico and adjacent parts of Arizona. 



These are the trees of which the forest is comi^osed, and which are 

 the sole reliance for construction and fuel. Of their value to the 

 country, of the importance to the country of their preservation, of the 

 «sad inroads that are made upon them by fires, and of their rapid con- 

 sumption by the inhabitants, especially in mining, it is superfluous here 

 to discourse. 



The few angiospermous trees are of quite inferior importance, and the 

 following are the only considerable ones : 



Cercocarpus ledifolms, called Mountain Mahogany, is peculiar to the 

 mountains of the Great Basin and of its borders. It is commonly a mere 

 shrub, but at between 6,000 and 8,000 feet on the mountain sides it forms 

 a small tree of 20 to 40 feet in height and a trunk which has in some 

 cases reached the girth of 7 feet at base. The wood " is of a bright 

 mahogany color, and susceptible of a beautiful polish, is exceedingly 

 hard, heavy, and close grained, but very brittle, and so liable to heart- 

 shake and difficult to work as to be useless in the arts. It is, however, 

 sometimes employed for the bearings of machinery, where it is found to 

 wear as well as metal." " It is," continues Professor Sargent, from 

 whom these extracts are taken, "probably the only North American 

 wood which is heavier than water," its specific gravity being deter- 

 mined by him to be 1.117 and its rate of growth so slow that " an exam- 

 ination of several specimens from one to two hundred years old shows 

 an annual increase of wood only one-sixtieth of an inch in thickness." 



Wegundo aceroides^ the Ash-leaved Majile, is found iu valleys along 

 water-courses in the southern part of the Rocky Mountains, and as far 

 west as the Wahsatch, and*south to New Mexico and Arizona, while in 

 California it is represented by a closely allied species. Its eastern ex- 

 tension is to Canada and the borders of New England. Sugar is some- 

 times made from its sap. 



More important and conspicuous are the Poplars, whicli, growing 

 wherever there is running water traversing even very arid districts, 



