LUTHER BURBANK 
Such is the explanation that the paleo-botanist 
gives us of the fact that the indigeneous vegetation 
of America to-day is closely similar to that which 
stocked the sub-arctic regions of the entire north- 
ern hemisphere in the geological period known as 
the Mesozoic—a period that seems infinitely 
remote when measured in terms of human history, 
yet which in the scale of time as measured by the 
geologist is relatively recent. 
Such trees as the sequoia, we are told, are sur- 
vivors of that ancient regime that chanced to find 
hospitable shelter on the western slopes of the 
Sierras. Similarly the tulip tree of the east, with 
the blossoms that seem anomalous for a tree, 
should be regarded as the souvenir of a past age— 
a lone representative of vast tribes that once flour- 
ished in tropical luxuriance in regions that now 
give scant support to moss and lichen and stunted 
conifers. 
All in all, we are told, the remaining vegetation 
of to-day, varied though it seems, is but a scant 
reminiscence of that of the period preceding the 
ice ages. Only a few species, relatively speaking, 
were able to make their migration rapidly enough 
to escane destruction. These included a certain 
number, Jike the sequoia and the tulip tree, that 
were able to reach coigns of vantage that per- 
mitted them to exist without changing essentially 
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