FLORA, 233 
the occurrence of identical species in distant parts of the 
world, would favour the view that countries with similar 
climates had originally many species of plants in common, 
In the case of grasses, we would naturally suppose that 
they must have been produced in their social state, 
forming pasture for the nourishment of animals ; and such 
we might conjecture to be the case with social plants in 
general. 
‘ Edward Forbes advocates strongly the view of specific 
centres, and endeavours to account for the isolation of cer- 
tain species or assemblages of plants from their centres, by 
supposing that these outposts were formerly connected, and 
have been separated, by geological changes, accompanied 
with the elevation and depression of land. Schouw opposes 
this. He thinks that the existence of the same species in 
far distant countries is not to be accounted for on the sup- 
position of a single centre for each species. The usual 
means of transport, and even the changes which have 
taken place by volcanic and other causes are inadequate, 
he thinks, to explain why many species are common to 
the Alps and the Pyrenees on the one hand, and to the 
Scandinavian and Scotch mountains on the other, without 
being found on the intermediate plains and hills; why 
the flora of Iceland is nearly identical with that of the 
Scandinavian mountains ; why Europe and North America, 
especially the northern parts, have various plants in 
common, which have not been communicated by human 
aids. Still greater objections to this mode of explanation, 
he thinks, are founded on the fact that there are plants at 
the Straits of Magalhaens, and in the Falkland and other 
antarctic islands, which belong to the flora of the Arctic 
pole; and that several European plants appear in New 
Holland, Van Diemen’s Land, and New Zealand, and 
which are not found in intermediate countries. Schouw, 
therefore, supposes that there were originally not one, but 
many primary individuals of a species.’ 
A writer in the Scotsman has called attention to the 
