ON TIMBER TREES 
recollection of these vicissitudes, can adapt itself 
to the inhospitable conditions of our modern cli- 
mate are but dwarfed representatives of ancient 
races of giants. To preserve life at all it was 
necessary for them to conserve their energies; and 
gigantic growth is feasible only for plants that can 
send their roots into rich, well watered soils and 
can likewise draw sustenance perennially from 
the atmosphere, unhampered by long periods of 
dormancy when life itself is threatened. 
But these dwarfed races carry in their germ 
plasm, submerged but not eliminated, factors for 
giant growth; factors for such development as 
would adapt them to life in the tropics; factors 
also for such development as would adapt them 
for life in the arctics. 
Their hereditary factors, in a word, are as 
varied as have been their past environments. So, 
as I said, what each tree is exteriorly gives us but 
faint suggestion of what it might be were its un- 
realized hereditary possibilities to be made 
actualities. 
So far as we know at present, the only way in 
which these unrealized possibilities may in any 
conspicuous measure be brought out is by hybrid- 
izing species that have so far diverged that they 
lie almost at the limits of affinity. By such union 
of hereditary factors that have long been dis- 
[191] 
