yes i ta 
1903] FLORA OF SOUTHERN CALIFORNIA 265 
must also be taken into consideration. It is believed, however, 
that the divisions here laid down will not be greatly modified 
when all the facts bearing on the problem come to be known. 
LIFE AREAS OF SOUTHERN CALIFORNIA. 
Provinces Regions Areas Subareas 
Arctic Alpine 
Boreal & P : 
Boreal 3 Hudsonian 
 * Canadian 
Transition Upper 
Lower 
Mojave 
Lower Sonoran Desert J 
Colorado 
Sonoran Interior 
Upper Sonoran Cismontane 
: Insular 
The various life-zones in an ideal section across southern 
California, from the lowest point in the deserts, across the highest 
mountain peak, to the coast islands, are represented below: 
IDEAL SECTIONAL DISPOSITION OF THE LIFE-ZONES. 
Alpine 
Hudsonian 
Canadian 
Upper Transition 
Lower Transition 
Juniperus Zone Pseudotsuga Zone 
Pifon Zone Interior Subarea 
Yucca Zone Coastal Subarea 
Larrea Zone Littoral Zone 
Atriplex Zone (?) Insular Subarea 
INTERRELATIONS OF THE DIFFERENT LIFE-AREAS. 
It is not to be understood that these various phytogeographi- 
cal subdivisions are strictly limited and sharply defined, as they 
are represented on biological charts. Here, as always, nature 
does not pass with abruptness from one formation to another; 
rather one shades gradually into another. Thus we find few, if 
any, species where boundaries are strictly conterminous. And 
in passing across the country a successive and continuous disap- 
