36 



VEGETATION OF A DESERT MOUNTAIN RANGE. 



** Humulus lupulus var. neomexicanus. 

 *** Hypericurn formosum. 

 *** Juncus brunnescens. 

 *** Juncus interior. 



** Limnorchis sparsiflora. 

 * Lister a sp. 



** Microstylis porphyrea. 

 *** Mimulus cardinalis. 

 *** Mimulus guttalus. 

 *** Osmorhiza nuda. 

 *** Oxalis metcalfii. 



** Oxalis wrightii. 



* Polygonum douglasii. 

 ** Pyrola chlorantha. 

 ** Pyrola secunda. 

 ** Rubus arizonicus. 

 ** Rudbeckia laciniata. 

 "** Scrophularia sp. 

 "** Smilacina amplexicaulis. 

 ** Smilacina sessilifolia. 

 Solanum fendleri. 

 Thalictrum fendleri var. wrightii. 

 Viola canadensis var. rydbergii. 

 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 



