58 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
These instances are not to be confused with those illustrated by 
plants of wide altitudinal range, like Castilleja miniata, which occurs 
in all the zones from Upper Sonoran to Arctic, as do also Castilleja 
angustifolia, Aquilegia formosa, Heracleum lanatum, Hypericum 
scoulert, Achillea millefolium, and others. 
The condition that has determined this strange nonconformity in 
the altitudinal or zonal relations of the species above mentioned is 
perhaps to be sought in the lower winter temperatures of the interior. 
This factor alone may tend to confine a species to the lowest zonal 
position in which it can maintain its existence. 
THE CANADIAN ZONE. 
This is the most illy defined of all the life zones in Washington, 
merging into the Transition below and the Hudsonian above. Its 
most characteristic tree is perhaps the western white pine (Pinus 
monticola), but in Washington this tree is not abundant. In the 
Olympic and Cascade mountains the amabilis fir (Abdes amabilis) is 
also a characteristic tree, as is its near relative, the noble fir (A. nobi- 
lis), found in the Cascades from Mount Stuart southward. Apart 
from these truly characteristic trees, the white fir (Abies grandis) 
and the western hemlock (7’suga heterophylla) (Pl. XVI) both find 
their best development in the Canadian zone, but both also are not 
rare at sea level. The dominant tree of the Humid Transition zone, 
the red fir, also thrives in the company of its Canadian relatives. 
On the eastern slopes of the Cascades, and more especially in the 
mountains of eastern Washington, two other trees appear in the Cana- 
dian zone, the Engelmann spruce (Picea engelmanni) and the western 
larch (Larix occidentalis) , while the amabilis and noble firs disappear. 
A characteristic plant association of this zone is that of the lodge- 
pole pine, a form of Pinus contorta, which often forms dense forests. 
The trees are remarkably uniform in size, seldom exceeding 1 foot in 
diameter and 60 feet in height. Such forests are often very exten- 
sive, the one species making up 90 per cent of the timber. While 
most abundant in the Canadian zone, groups of the lodgepole pine 
occasionally occur isolated in yellow pine forests. 
There are but few plants in Washington confined to the Canadian 
zone. The somber depths of these moist forests, however, induces a 
luxurious carpet of mosses and a vegetation which is largely erica- 
ceous. Among the more plentiful shrubs are the blue huckleberry. 
(Vaccinium ovalifolium), Menziesia ferruginea, Pachystima myrsi- 
nites, the trailing Rubus nivalis, and the dwarf cornel (Cornus 
canadensis) . 
