FLORA OF THE SAN ANTONIO MOUNTAINS 



75 



The Transition Zone, usually found between 5500 and 8000 feet 

 altitude, is for all practical purposes coincident with the occur- 

 rence of Pinus ponder osa and its variety Jeffreyi. The Transi- 

 tion, like the Upper Sonoran Zone, has been conveniently divided 

 into two parts. The upper, which usually lies above 6750 feet 

 altitude, has been designated as the Upper Transition Zone and 

 is characterized by the dominance of Abies concolor and Pinus 

 Latnbertiana. To the lower part, where typical Pinus ponderosa 

 is most abundant, the name Lower Transition Zone has been 



Fig. 2. A forested slope in the Canadian Zone, on the south spur of Baldy at 



about 9000 feet altitude 



applied. The following list of perennials appear to be restricted 

 to the designated divisions of the Transition Zone. 



Plants restricted to the Lower Transition 



Zone 

 Sitanion minus californium 

 Eriogonum umbellatum 

 Lupinus Grayi 

 Arctoslaphylos Parryana 

 Chcenaclis santolinoides 

 Brickellia microphylla 



Plants restricted to the Upper Transition 



Zone 

 Sisyrinchium oreophilum 

 Carex aurea celsa 

 Salix cordata Watsoni 

 Eriogonum Wrightii subscaposum 

 Arabis repanda 

 Adenostegia Nevinii 

 Sambucus glauca velulina 



THE PLANT WORLD, VOL. 22, NO. 3 



