LUTHER BURBANK 
which now, age on age, became less and less bright 
as the earth changed the direction of its axis. 
Of course there were other trees that did not 
undergo this modification. But these were forced 
either to make more rapid migrations to the south 
or to give up the fight altogether and to submit to 
extermination. The only ones that were able to 
maintain existence in the regions where the cli- 
mate became exceedingly cold were those that had 
developed the new type of leaf-form, and had 
learned to conserve their energies to the last 
degree. 
But of course the trees that took on this new 
habit varied among themselves, and as they spread 
to different regions such variations were developed 
and fixed under the influence of different environ- 
ments, until many tribes of needle-leaved trees 
were developed so differently as to constitute the 
races that the modern botanist terms pine and 
spruce and cypress and juniper and hemlock and 
yew and cedar. 
Representatives of all the chief genera of coni- 
fers have recognized a place among ornamental 
trees and are everywhere popular in cold climates. 
The variations among the different species are so 
obvious as to attract the attention of the least 
observant. And the opportunity to develop any 
fixed new form is correspondingly good. 
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