J. D. Hooker, Introductory Essay to the Flora of Tasmania. 238 
great a reduction of the temperature of the globe as should hav 
allowed the preglacial temperate flora to cross the Equator in 
= any longitude. It is evident that, under such cold, the most 
* The question of the state of the mean temperature of the globe during com- 
paratively recent geological periods is yearly derivi er importance in rela- 
tion to the problem of distribution. Upon this point geologists are not altogether 
ith the masters of physical science. Lyell (Principles, ed. ix, 
t of any m: 
induced the glacial epoch, A third theory is that such a redisposition of land and 
peg Would induce a glacial epoch in our hemisphere need not be great, nor neces- 
a decrement of the mean temperature of the whole earth. 
