578 The American Naturalist. [July, 
portion of it. The story has been often told, but one 
aspect of it will deserve further attention. Out of the various 
forests of north temperate regions, we may recognize four that 
are of peculiar interest. The European, the Northeast Asian, 
the Appalachian, and the Pacific North American. All are 
relics of the preglacial northern forest, but they are relics in 
very different stages of preservation. The Northeast Asian is 
a marvel to students of tree-life in the abundance and im- 
mense variety of its forms. Evidently it has best preserved 
the characters of the primaeval forest. The poverty of the 
European forest is equally striking and has been well ex- 
plained by the fact that the east and west mountain chains 
and the Mediterranean to the south were fatal to the vegetation 
retreating before the advancing glaciers. The Atlantic North 
American, or Appalachian forest, on the contrary, was well 
preserved by the physical characters of the country, and in its 
perfection is second only to the Northeast Asian. But the 
Pacific North American is an anomaly. It is preeminently a 
forest of Conifers with an astonishing poverty of hardwood 
types, although the latter are abundant as fossils in the Ter- 
tiary strata of the region. But is this such an enigma as it 
has often been considered? ‘The ice sheet that swept over the 
Great Lakes and down into the Mississippi Valley did not 
reach that Pacific forest region of the United States, but its 
influence was felt there none theless surely. Before it retreat- 
ed—first the Hardwood forest, and close on its heels the Coni- 
ferae. The Coniferae invaded the strip along the western 
slope of the Rockies, and also the great Northeastern Asian 
forest region, and remained in both, about equally strong in 
number of species. But in the case of the first named region 
what became of the Hardwood forest that pushed ahead of the 
Conifers? Behind it on the east were the Rockies ; before it 
on the west the Pacific; and to the south the stern physio- 
graphie obstacles of the Mexican coast. And again, what 
was the character of the coniferous forest that invaded the 
Pacific strip? We need only point to the two Sequoias, sem- 
pervirens and gigantea, the * Big Trees" of California, the 
culminating triumphs of vegetative energy in Coniferae. The 
