Flora of the Pacific Mountain Ranges, 961 
are little less gigantic than the big trees of the Sierra Nevada, and a thousand 
times more numerous. Through most of California, these two Pacific forests 
are distinct but in the northern part of that state, they join and form one 
rich woodland belt skirting the Pacific and extending through British Columbia 
into Alaska. To these forests, we must now turn our attention. 
ASA GRAY long ago called attention to the fact that the Pacific forest has 
no Magnolias, no tulip-tree, no linden and is very poor in maples; no locust 
trees, nor any leguminous trees; no cherry large enough for a timber-tree, 
like the eastern wild black cherry; no gum trees (Nyssa, nor Liguidambar), 
nor sorrel-tree, nor Aalmia, no persimmon or Bumelia; not a holly; only 
one ash that may be called a timber-tree; no catalpa or sassafras; not a single 
elm or hackberry; not a mulberry, nor planer-tree, nor Maclura; not a hickory 
nor a beech, nor a true chestnut, nor a hornbeam; barely one birch tree, 
and that only far north, where the differences are less striking. But as to 
coniferous trees, the only missing type is the eastern Tarodium distichum‘). 
5. Flora of the Pacific Mountain Ranges. 
General Remarks. The Pacific forest consists of conifers, with non-coni- 
ferous trees as an occasional undergrowth, or as scattered individuals, and con- 
Spicuous only in valleys, or in the sparse tree-growth of the plains, on which 
the oaks form open groves. This predominance of coniferous vege- 
tation is remarkable and paradoxic. The Pacific coast is the sole refuge of 
the most characteristic and wide-spread types of Miocene coniferae, the sequoias. 
Any attempted explanation of this extreme paucity at present of broad-leaved 
trees, which existed in the form of magnolias, beeches, chestnuts, elms and 
gums Ziguidambar down to the beginning of the glacial period as shown by 
remains in the auriferous gravels of the west, bristles with difficulties. Much 
may be attributed to glaciation; something to the tremendous outpours of lava; 
much to the narrowness of the forestbelt, to the want of a summer rain, and 
t0 the most unequal and precarious distribution of that of winter. The coni- 
ferous trees essentially xerophytic in constitution were better able to survive 
when subjected to a combination of such influences, while the broad-leaved 
trees typic of the Miocene forest succumbed when exposed to the conditions 
Which the conifers were able to resist. This suggests that the difference 
between the forests of the east and west is to explained by the climatic and 
other conditions which existed during and at the close of the great ice age, 
when the conditions which preserved the broad-leaved species of the east were 
exactly the reverse of those which in the Pacific coast brought about their 
extinction and the preservation of the coniferous vegetation, which is there 
dominant at the present day. ; 
The following Pacific coast trees have migrated into the Rocky Mountain 
Tegion and some have entered from the south (see ante). 
1) GRAY, Asa: Forest Geography and Archaeology. Americ. Journ. Science and Arts XVI. 1878. 
