10 University of California Publications in Botany. [ VOL - 3 



The Hudsonian and Canadian zones cannot be clearly dis- 

 tinguished from each other in Southern California, but together 

 they occupy the rather narrow belt between timber line and the 

 extensive forests of Yellow Pine (Pinus ponderosa, including its 

 variety Jeffrey i) and White Fir (Abies concolor). Their most 

 characteristic trees with us are the Limber Pine (P. flexilis) and 

 the Murray Pine (P. Murrayana), the latter frequently occupy- 

 ing boreal islands completely surrounded by Transition Zone 

 elements. Perhaps none of our Compositae are restricted abso- 

 lutely to these zones. 



The Transition Zone is best marked by the presence of Yellow 

 Pine and White Fir. It is sometimes convenient to speak of a 

 Lower Transition, where the pine is dominant, and of an Upper 

 Transition, where the fir is dominant. Many Compositae are 

 restricted in their distribution to this zone, the list including the 

 following : 



Haplopappus gossypinus Eriophyllum lanatum obovatum 



Aster Fremonti Parishii Helenium Bigelovii 



Aster delectabilis Arnica Bernardina 



Hemizonia Wheeleri Crepis acuminata 



Homizonella minima Hieraceum albiflorum 



The Upper Sonoran Zone is essentially co-limital with the 

 chaparral belt, but also includes the Piiion belt of the desert 

 ranges, Mt. Pinos, etc. It occupies nearly all of the Cismontane 

 Area, that is, the area west and south of the San Gabriel, San 

 Bernardino, San Jacinto, and Cuyamaca Mts. Common elements 

 indicative of this zone are Chamiso (Adenostoma fasciculatiim), 

 Wild Buckwheat (Eriogonum fasciculatum) , Beard-tongue 

 (Pentstemon antirrkinoides) , Deer-weed (Lotus gldber), etc. Of 

 the Compositae restricted to this zone may be mentioned : 



Ericameria ericoides Artemisia California 



Ericameria pinifolia Carduus occidentalis 



Baccharis pilularis Perezia microcephala 



Encelia Calif ornica Malacothrix saxatilis 



Eriophyllum Nevinii Hieraceum Parishii 



The Lower Sonoran Zone occupies the Desert Area with the 

 exception of those ranges which extend into the Upper Sonoran. 

 Certain warm areas west of the mountains are perhaps also best 

 classified as Lower rather than Upper Sonoran, noticeably a 



