Cascade- and Coast ranges. 263 
have been influential. One explanation based on the historic development of 
the flora here is that the northward migration of caniferous and other trees 
on the Pacific coast has been checked by the long persistence of numerous 
local valleys glaciers which descend from the mountains to the sea. Another 
explanation advanced by FERNOW °') seems plausible in addition to the reason 
given above. The Alaska peninsula and Aleutian islands show evidence that 
they are of recent and volcanic origin. A forest could come to them only 
from the east, or northeast, by the gradual extension of the coast forest. To 
secure this extension, it is necessary that the winds should blow from the north 
and east from September to May, when the spruce and hemlock release their 
seed. The contrary usually happens; there is during these months a constant 
succession of southeast and south winds and the air is heavily charged with 
moisture bad for wind blown seeds. For these reasons, the spread of the 
forest has been retarded. 
Cascade- and Coast ranges. This forest of Alaska is a continuation of the 
great maritime forest of north-western America, which at the south 
embraces the redwoods of California and spreads over western Oregon and 
Washington. This forest resembles the forest of Puget Sound and of western 
British Columbia, but it lacks Pseudotsuga Douglasii (P. taxifolia), the most 
abundant tree about Puget Sound, Adies grandis and Acer macrophyllum 
abundant in all the coast region further south. It represents historically and 
floristically a forest extension which began with the final recession of the great 
ice sheet and has continued ever since’). 
At Puget Sound the character of the forest, although due to coniferous 
trees, owes its individuality to new species, which appear and which probably 
represent the northwestern fragment of that great forest which covered North 
America in Miocene times with the extinction of the majority of broad leaved 
trees. In the Puget Sound region, where the Cascade and Coast ranges Ag 
we find the following trees to make up a forest which for denseness and size 
of its individual trees stand unrivalled. 
East and southeast of Puget Sound in a territory well 
are the Washington and the Mount Rainier national forests. 
forests have been noted the trees given in the table below. 
and not in the Washington). 
watered by streams 
In these national 
(* in the Rainier 
folia Poir. — P. mucronata Sudw.). River bottoms to lower mountain 
Bench lands of the valleys and slopes. 
lower mountain slopes. | 
Pseudotsuga Douglasii Carr. (= P.taxi- | Thuja plicata Don. 
ı) Fernow, B. E.: The Forests of Alaska. Forestry and Irrigation. VII: - Feb. ur 
2) The vegetation of the northwest coast region is probably nowbere Bu highly develope 
than in the Queen Charlotte islands of the coast of Brit. Columbia. Of coniferous . at least 
Seven species are found, viz., Picea sitchensis, Tsuga heterophylla, au Mertensiana, Thuja 
Plicata, Chamaecyparis nootkaönsis, Pinus contorta and Taxus brevifolia. 
