30 NORTH AMERICAN FAUNA. {wo. 16. 
covered with dwarf trees is that these slopes are in their zone position 
truly alpine and above timberline, as already explained. 
Nothing is easier than to refer to the wrong zone species found in the 
treeless basins between the pine-covered ridges. But when it is under- 
stood that parts of each basin, regardless of the distance below the 
highest tongue of timber, are unquestionably abore timberline (and con- 
sequently Alpine) and that other parts, regardless of the distance above 
the nearest trees in the basin, are unquestionably well below timberline 
(and consequently Hudsonian), mistakes of this kind will be less 
frequent. 
THE FORESTS OF SHASTA. 
Shasta rises from a forested region (pl. v), and the mountain itself is 
continuously forest-covered up to an altitude of 7,500 or 8,000 feet. The 
trees of the lower slopes are those of the surrounding region, but those 
of the middle and upper slopes belong to such widely different species 
that it is necessary to divide the mountain forest into three belts, which, 
from their most distinctive trees, may be designated (1) the lower or 
yellow-pine belt; (2) the middle or Shasta fir belt, and (3) the upper or 
white-bark pine belt. It is interesting to observe that these forest 
divisions, as shown later, coincide with the three Life zones—the 
Transition, Canadian, and Hudsonian. 
(1) The Lower Belt or Belt of Yellow or Ponderosa Pines (Pinus ponderosa). 
The most abundant and characteristic tree of the lower slopes and 
surrounding region is the yellow or ponderosa pine, which forms a con- 
tinuous open forest up to an altitude, on the south and west sides, of 
about 5,500 feet. The ouly material gap in the pine belt of the moun- 
tain proper is a strip about 8 miles in length on the cold northeast 
quadrant, which is occupied by lodge-pole pines belonging to the zone 
above (Canadian zone), 
On the south and west the open pine forest of the basal slopes is 
interrupted by extensive parks, which from a distance appear to be 
meadows of waving grass. A nearer view shows this to be an illusion, 
the broad fields of green being in reality impenetrable thickets of 
chaparral—a chaparral of unyielding manzanita and buck brush 
(Arctostaphylos patula and Ceanothus relutinus, see fig. 15). 
Northwest of Shasta the yellow-pine forest is interrupted by the open 
plain of Shasta Valley, which on the southwest ends abruptly at the 
town of Edgewood. North, northeast, and east of Shasta the ponder- 
osa pine forest continues with unimportant interruptions to Devils 
Garden, (ioose Lake, and the Madeline Plains; on the south it is prac- 
tically continuous to the base of Lassen Butte, and thence along the 
flanks of the Sierra for 350 miles; on the southwest it follows the canyon 
of the Sacramento River to a little below Delta, where, in the bottom 
of the canyon and on its warmer slopes, the curious digger pines of 
the Upper Sonoran zone mix with and soon replace the ponderosa pines 
