Great Basin: Arizona- New Mexico District. 581 
and Chisos Mountains it ranges as high as 6000 feet (1830 m). On the steep 
and slopes of these mountains the difference of zone level on opposite sides is 
often 2000 or 3000 feet, increasing with the steepness and barrenness of the 
slope. Some of the most characteristic plants are Pinus edulis, P. cembroides, 
Funiperus pachyphloea, F. monosperma, F. flaccida, Quercus grisea, O. Emoryi, 
Adolphia infesta, Nolina texana, Mimosa biuncifera, Cercocarpus parvifolius, 
Fallugia paradoxa, Yucca Sncchta, Agave Wizlizeni, A. applanata'). 
/pper Coniferous Forest Formation. The characteristic tree of this belt is 
Pinus ponderosa (Pinus ponderosa Facies) which forms one of the most 
beautiful forests in existence, above an altitude of 7000 feet (2100 meters) and 
extends up as high in some of the parks as 8800 feet (2675 meters). As a 
distinctive species, however, it loses its character at about 8200 feet (2500 meters) 
where it is invaded and soon after replaced by Pinus flexilis, Pseudotsuga 
Douglasüu and Populus tremuloides, Quercus Gambelii grows in clumps with 
the bull pine at an elevation of 8000 feet. The herbaceous plants of this belt 
are Campanula Parryi, Frasera speciosa, Gilia aggregala, G. attenuata, Oxy- 
baphus angustifolius (Allionia linearis), Oxytropis Lamberti. 
This forest belt reaches its highest development about San Francisco 
Mountains. From here it stretches north to and beyond the Grand Canyon 
of the Colorado River westward to Bill Williams Mountain and southward to 
the rim where the Colorado Plateau breaks down to the southern plains. 
the Sacramento, White, Capitan and Jicarilla Mountains the belt of 
Pinus ponderosa ranges from 6400 to 9000 feet. The principal trees are with 
the main pine Pseudotsuga Douglasii, Abies concolor, Mexican white pine, Pinus 
strobiformis and Quercus undulata. Along the streams and canyons are Robinia 
neomexicana, Acer grandidentatum, Populus angustifolia, and other deciduous 
species overlapping from the pihon belt. 
Growing with the main pine on the Mazatzal Mountains at the higher 
elevations are scattered specimens of Pinus flerilis, Abies concolor, Pseudotsuga, 
while Pinus edulis exists at lower elevations. In the White Mountains the 
same general disposition seems to prevail while Cupressus arizonica lines the 
canyons. In Texas a pine forest formation exists on the higher Guadalupe 
and Davis Mountains”). The chief elements of the formation are Pınus pon- 
derosa on Guadalupe Peak at 9000 feet and on Davis Mountains. Next 
to this prevalent pine is Pseudotsuga Douglasii, Pinus flexilis, while on the 
lower slopes are P. edulis, Funiperus pachyphloea, Quercus Emoryi (in the 
Canyon), ©. Gambelii. 
A few of these reach the summits of the highest mountains in the great 
bend of the Rio Grande River in Western Texas, but scarcely in force to 
er the Mexican i. e. upper Sonoran character of me flora. This belt 
1) BAILEY, VERNON! Biological Survey of Texas, 1905. 
2) Brav, W. L.: The ecolog. Rel. of Vegetation of Western Texas, 1901.  Havarp, V.: 
Flora of western and southern Texas, 1885. 
