338 fegetation in Nevada and Arizona. [June, 
of Conifere, while the lower line rests upon a belt (400 feet of 
the vertical section) of mountain mahogany ( Cerocarpus ledifo- 
lius), which in turn gives place at 7000 feet to the belt of Sali- 
cacee. This group terminates irregularly at the beginning of 
the foot-hills, at an elevation of about 6200 feet. The foot-hills 
are chiefly covered with Phlox, Lupinus, and Rosacee, and the 
plain with “ grease-wood ” (Sarcobatus vermiculatus) and “ sage- 
brush ” (Artemisia tridentata), the former being greatly in ex- 
cess, but is gradually replaced by the latter going southward. 
The lines of demarcation are frequently indistinct, owing to the 
mingling of species of one belt with the adjoining ones, but they 
are plain enough to obtain an average elevation which I shall 
adopt in these descriptions. 
At Prospect Hill, the timber-line has risen to 9400 feet in alti- 
tude ; the belt of mountain mahogany becomes narrower, giving 
place at 8000 feet to the Salicacee, which belt becomes broader 
and terminates below at an elevation of 7000 feet. As the level 
of the plain is 6000 above the sea, there are 1000 feet to be ac- 
counted for. The plain contains more Artemisia tridentata, and 
A. filifolia in place of Sarcobatus vermiculatus to a very great 
extent, the latter being found on the lower foot-hills, above 
which we find but little Phlox, some Lupinus, and more Rosacee 
and Composite. There is here a great increase in elevation of 
similar species over those at Bull Run. 
Again, at Belmont the Conifere end with the timber-line at 
9700 feet, and where the belt of the Salicacee begins but a seam 
of scattering mahoganies is found, the place having been taken 
up by a wider belt of Conifere above and of Salicacee below. 
On the plains south of Belmont more saline matter is found in 
the soil, giving rise gradually to a more desert-like vegetation. 
Artemisie are less numerous, and are replaced by Algarobia 
glandulosa, the former occurring abundantly on the foot-hills, 
upon the upper slopes of which Cactacew now make their ap- 
pearance. At Mt. Nagle and, just south of it, at Mt. Macgruder, 
there is little variation of elevation of the flora, so that at the 
latter the timber ceases to grow at 11,150 feet (covering the 
summit of Mt. Nagle at an altitude of 11,000 feet), the belt of 
Conifer running down to 8500 feet; when the belt of Salicacew 
occupies the space down to an elevation of 8100 feet above the sea. 
The belt of the Composite now rests upon one of Yucca buccata 
and F. angustifolia, which, farther down on the foot-hills, a, oe 
placed by Cactacee, and on the desert by the Artemisia triden- 
