1903] FLORA OF SOUTHERN CALIFORNIA 215 
have been added to the short list. Further explorations may be 
expected to increase it, but not greatly. 
-THE NEVADAN AREA. 
The lower limit of this area coincides with that of Pinus 
ponderosa. On cismontane slopes this is seldom below 5,000* 
1,504") altitude; but on the opposite side the influences of the 
desert force it up to 6,000" (1,828™), and even to 7,000" 
(2,133™) above sea level. This region contains the only real 
forests in the entire territory, and while these are far inferior to 
those in the damper and cooler parts of the Pacific Coast, they 
are by no means insignificant, either in extent, or in the size and 
variety of the trees which compose them. 
_ As already stated the zones which I have included in this 
area are much confused. Perhaps the best marked is the Hud- 
sonian, which we may consider as indicated by the presence of 
Pinus flexilis. This is known to occur on Grayback, San Jacinto, 
and Santa Rosa peaks, and it should be found on one or two 
other high summits. As a zonal index its proper limit would be 
between 9,000 or 10,000 to 12,000" (2,750-3,650™). But 
under favorable conditions it descends 1,000-2,000% (300- 
600™) lower into the Canadian, and in at least one instance an 
isolated Hudsonian “island” occurs at 6,500" (1980™), well 
down in the Neutral or Transition zone. 
The Canadian zone, which may be taken as indicated by Pinus 
Murrayana, is even less definitely marked. This pine is not 
uncommon in places as low as 6,500* (1,980™), but it is better 
developed in moist valleys 1,000-2,000* (300-600™) higher, 
and becomes more abundant as one ascends, until it mingles 
with the limber pine of the superior zone. 
But the most important zone is the Neutral, or Transition ; 
and it is the only one represented in the greater part of the 
Nevadan area. The principal tree throughout this zone is Pinus 
ponderosa. Its lower limits have been specified, and its upper 
limit may be placed at 8,500 (2,590™), or occasionally, and 
under favoring conditions 500-1,000* (150-300™) higher. 
**For an account of this see “The Flora of Snow Cajion, California,” by the 
writer, in Plant World 4: 227. 
