VEGETATION OF THE SANTA CATALINA MOUNTAINS. 25 
relatively little activity is observable in May and June, at least away 
from arroyos and springs. In the Upper Encinal the early months of 
spring partake of the rest which is then predominant in the Forest 
region. The deciduous trees begin foliation in late April or early May 
and some of the root perennials are not far behind them in their earliest 
activity. The duration of the arid fore-summer being slightly less in 
the Upper Encinal than in the Lower Encinal, and its intensity being 
also less, there is not so decided a break, among the herbaceous peren- 
nials between the first activity of spring and that of the humid mid- 
summer, as there is in the Lower Encinal and the Desert. 
THE LOWER ENCINAL. 
The species which chiefly characterize the Lower Encinal at its 
desert edge have already been mentioned: Quercus oblongifolia, Quer- 
cus arizonica, Juniperus, Vauquelinia, Dasylirion, Nolina, Yucca macro- 
carpa, Arctostaphylos pungens, Agave palmert, and Agave schottii. All 
of these are much more abundant at 5,000 feet than at 4,500 except 
Quercus oblongifolia, which is a tree of very narrow vertical range, rarely 
occurring above 5,200 feet and reaching its limit at 5,600 feet on steep 
south slopes. At 5,000 feet the Encinal has been augmented by the 
appearance of the common trees Quercus emoryt and Pinus cembroides 
(pifion) and by the shrubs Garrya wrightii, Mimosa biuncifera, Rhus 
trilobata, and Rhamnus crocea var. pilosa (see plates 11a, 15, and 16). 
The only characteristic Desert species which persist throughout the 
Lower Encinal are: Carnegiea gigantea, a single young individual of 
which has been seen at 5,100 feet; Opuntia versicolor, which reaches 
5,500 feet; Fouquieria and Echinocactus wislizeni, which reach 5,600 
to 5,800 feet; and Mamullaria grahami, which ascends to 7,000 feet. 
So far as known, no other plants occurring on the Bajadas or in any 
of the other non-palustrine desert habitats range to elevations above 
6,000 feet.* There are at least a few species found in cafions and near 
constant water which range from the elevation of the Desert to more 
than 6,000 feet. Several of the typical desert genera are represented 
at higher elevations by species which seldom range as low as the Upper 
Desert region. Two species of Opuntia (platopuntias) are found 
throughout the Encinal, growing in thin soil or on rocks, and reaching 
their highest occurrence solely on ridges or upper slopes. One of these 
species has been found on a sharp rocky ridge at 7,200 feet, which is 
the highest known occurrence of a platopuntia in the Santa Catalinas. 
Mamillaria arizonica ranges from the Upper Desert to nearly 7,000 
feet; Echinocereus polyacanthos ranges from about 5,000 feet to 7,800 
feet, which is the highest elevation at which any cactus has been found 
in these mountains. Agave palmerit and Yucca schottii are also fre- 
* This statement is made only with respect to the Santa Catalinas. The influence of the 
character of the underlying rock and of the elevation of the surrounding desert each serves to 
determine indirectly the vertical limits of desert species. 
