90 VEGETATION OF A DESERT MOUNTAIN RANGE. 



Robinia neomexicana ranges through 3,800 feet, from its lowest occur- 

 rence on flood-plains near constant water at 5,300 feet, to its highest 

 occurrence on dry ridges near the summit of Mount Lemmon at 9,100 

 feet. On the higher mountains of southern Arizona this species ascends 

 to over 10,000 feet. Amorpha californica, after the manner of Vitis, 

 ranges 3,500 feet from moist arroyos at 4,200 feet to dry ones at 7,700 

 feet. Agave palmeri ranges from dry slopes of east or west exposure at 

 3,200 feet to open ridges and crevices of rock at 7,400 feet, a belt of 

 4,200 feet. Among the species which reach neither the Bajada nor 

 the top of the mountain there are no others with vertical extensions 

 of more than 4,000 feet. An extreme range of 3,700 feet is possessed 

 by Juniperus pachyphlcea, from northern slopes at 4,200 feet to ridges 

 at 7,900 feet. Nolina microcarpa extends from 3,750 feet on north 

 slopes to 7,200 feet in open pine forest, a range of 3,450 feet, and Dasy- 

 lirion wheeleri from 3,600 feet to 6,600 feet, on opposing slopes, a range 

 of 3,000 feet. 



Among other plants which occur chiefly in the Encinal Region there 

 are none with vertical ranges in excess of 3,000 feet, few in fact approach 

 that range. Pinus cembroides extends from north slopes at 5,000 feet 

 to open rocky ridges at 7,800 feet, a range of 2,800 feet; Agave schottii 

 ranges from 3,700 to 6,000 feet, a belt of 2,300 feet; Garrya wrightii 

 ranges from 4,300 to 6,500 feet, an extent of 2,200 feet; and Quercus 

 emoryi extends from north slopes at 4,300 feet to south slopes at 6,200 

 feet, a vertical range of 1,900 feet. 



Among the plants which have their lowest occurrence in the flood- 

 plains of the Encinal and their principal range through the Forest 

 Region, a number have vertical belts of occurrence of more than 3,000 

 feet. Pinus arizonica itself is found through 3,300 feet and its upper 

 limit is determined only by the height of the mountain. Pseudotsuga 

 mucronata is found through 3,100 feet, and is also terminated by the 

 summit of the mountain. Quercus hypokuca and Quercus reticulata are 

 found through nearly 3,000 feet, and this extent of vertical range is 

 attained by a large number of herbaceous perennials of the Upper 

 Encinal and Forest. 



The Desert species which are encountered at the foot of the mountain 

 do not begin their vertical ranges at that point, and statements of the 

 elevations which they reach on the mountain are not to be compared 

 with figures for the ranges of Encinal and Forest plants. Mamillaria 

 grahami reaches the attenuated limit of its occurrence at 7,000 feet, 

 Echinocadus wislizeni at 5,600 feet, Fouquieria spkndens at 5,600 feet, 

 Opuntia versicolor at 5,500 feet, and Carnegiea gigantea at 5,100 feet. 

 Very few other species of the bajadas and desert hills are found above 

 4,700 feet. 



Among the most restricted vertical ranges of any plants which reach 

 neither the foot nor the summit of the mountain are those of Quercus 



