FOREST GEOGRAPHY AND ARCHZOLOGY. 229 
Wherefore the high, and not the low, latitudes must be 
assumed as the birthplace of our present flora;! and the 
present arctic vegetation is best regarded as a derivative of 
the temperate. ‘This flora, which when circumpolar was as 
nearly homogeneous round the high latitudes as the arctic 
vegetation is now, when slowly translated into lower latitudes, 
would preserve its homogeneousness enough to account for 
the actual distribution of the same and similar species round 
the world, and for the original endowment of Europe with 
what we now call American types. It would also vary or be 
selected from by the increasing differentiation of climate in 
the divergent continents, and on their different sides, in a way 
which might well account for the present diversification. 
From an early period, the system of the winds, the great 
ocean currents (however they may have oscillated north and 
south), and the general proportions and features of the conti- 
nents in our latitude (at least of the American continent) 
were much the same as now, so that species of plants, ever so 
little adapted or predisposed to cold winters and hot summers, 
would abide and be developed on the eastern side of conti- 
nents, therefore in the Atlantic States and in Japan and 
Mandchuria ; those with preference for milder winters would 
incline to the western sides ; those disposed to tolerate dryness 
would tend to interiors, or to regions lacking summer rain. 
So that, if the same thousand species were thrust promiscu- 
ously into these several districts, and carried slowly onward 
in the way supposed, they would inevitably be sifted in such a 
manner that the survival of the fittest for each district might 
explain the present diversity. 
Besides, there are re-siftings to take into the account. The 
Glacial period or refrigeration from the north, which at its 
inception forced the temperate flora into our latitude, at its 
culmination must have carried much or most of it quite be- 
yond. ‘To what extent displaced, and how far superseded by 
1 This takes for granted, after Nordenskjold, that there was no pre- 
ceding Glacial period, as neither paleontology nor the study of arctic 
sedimentary strata afford any evidence of it. Orif there was any, it 
was too remote in time to concern the present question. 
