( Ix) 
Prof. Thistleton Dyer, F.R.S.,in an admirable lecture on 
‘Plant Distribution as a Field for Geographical Research,’* 
admits three primary floras :— 
1st. The Northern Flora, practically the same as Hemsley’s 
northern region, which he divides into— 
la. The Arctic Alpine. 
1b. The Temperate. 
1c. The Mediterraneo-Caucasian. 
2nd. The Southern Flora, divided into— 
2a. The Australian. 
2b. The South African. 
2c. The Temperate South American. 
2d. The Antarctic Alpine. 
8rd. The Tropical Flora, divided into — 
8a. The Asiatic. 
3b. The American. 
8c. The African. 
There is really no great difference between the views of these 
three most competent authorities, except in the value that is 
attached by them to primary and secondary divisions. 
Hooker, it is true, whose personal knowledge, gained by travel 
in many of these regions, which alone will enable ‘a man 
to appreciate the physical features of the earth’s divisions in 
the highest degree, seems to consider the north temperate 
regions of the old and new world as divisions of primary 
importance, and in this agrees with most zoologists: whilst 
Dyer and Hemsley agree in uniting them. But, judging 
from the study of butterflies alone, I say without hesitation 
that the Nearctic and Palearctic regions are inseparable, and 
that the Nearctic region has fewer peculiar endemic genera 
and species than the Mediterranean-Asiatic, or, as I call it, 
_ Mediterraneo-Persic sub-region ; and, in consequence, I believe 
that the Nearctic or North Temperate region of the new world, 
is at best a sub-region or province of the great Temperate or 
Palearctic region. It is true that a number of species and 
some genera occur all over the United States, which are not 
Palearctic, and that in the Gulf States, New Mexico, 
* Proc. Royal Geogr. Soc., vol. xxii, 1878. 
