FOREST GEOGRAPHY AND ARCHZOLOGY. 2838 
the period of refrigeration, deeply covered a very large part 
of the forest-area ; much to the narrowness of the forest-belt, 
to the want of summer rain, and to the most unequal and 
precarious distribution of that of winter. 
Upon all these topics questions present themselves which 
we are not prepared to discuss. I have done all that I could 
hope to do in one lecture if I have distinctly shown that the 
races of trees, like the races of men, have come down to us 
through a prehistoric (or pre-natural historic) period ; and 
that the explanation of the present condition is to be sought 
in the past, and traced in vestiges and remains and survi- 
vals; that for the vegetable kingdom also there is a veritable 
Archeology. 
