“36 VEGETATION OF A DESERT MOUNTAIN RANGE. 
bik . neomexicanus. * Polygonum douglasii. 
ee oe es os ** Pyrola chlorantha. 
*** Juncus brunnescens. ** Pyrola secunda. 
*** Juncus interior. ** Rubus arizonicus. 
** Limnorchis sparsiflora. ** Rudbeckia laciniata. 
* Listera sp. *** Scrophularia sp. 
** Microstylis porphyrea. *** Smilacina amplexicaulis. 
*** Mimulus cardinalis. ** Smilacina sessilifolia. 
*** Mimulus guitatus. ** Solanum fendleri. 
*** Osmorhiza nuda. *** Thalictrum fendleri var. wrightit. 
*** Oxalis metcalfit. *** Viola canadensis var. rydbergit. 
** Oxalis wrightit. *** Viola nephrophylla. 
FLORA OF THE SANTA CATALINA MOUNTAINS. 
The wide range of physical conditions embraced within the area of 
the Santa Catalina Mountains gives them a relatively large flora, which 
has been estimated by Professor J. J. Thornber to be about 1,500 
species. Although the exploitation of this flora is not completed it is 
nevertheless sufficiently well advanced to show that elements are pres- 
ent which are common to each of many diverse regions lying north, 
south, east, and west. 
The desert at the foot of the mountains stands in unbroken connec- 
tion with the deserts of Sonora and Sinaloa. The Encinal and Forest 
regions, on the other hand, are isolated from other areas possessing the 
same physical conditions. Areas of Encinal are numerous and near, 
both on the low desert mountains and on the elevated plains of southern 
Arizona; while bodies of forest are to be found only at greater distances 
and more remotely separated from each other. The floristic history 
of the Encinal and Forest regions of the Santa Catalinas is quite as 
intimately bound up with the controlling influences of climatic con- 
ditions as is the present limitation of the vegetation. In fact the floras 
of the two isolated regions are a resultant between the physical con- 
ditions which they have presented in the remote and recent past and 
the operation of natural agencies of dispersal. 
PHYTOGEOGRAPHIC RELATIONSHIPS OF THE FLORA. 
It would not be within the scope of this paper to enter upon a detailed 
discussion of the floristic relationships of the isolated mountain areas 
of Encinal and Forest in southern Arizona, even if all the evidence 
bearing on such a discussion were now in hand. It will be instructive, 
however, to point out very briefly some of the principal floristic rela- 
tionships of the Santa Catalinas in order to demonstrate the extensive 
and diversified area over which members of its flora may be found. 
THE DESERT FLORA. 
The flora which occupies the bajadas of the Santa Cruz valley and 
the lower slopes of the Santa Catalina Mountains derives many species 
from each of two Mexican desert regions, the one lying at low elevations 
