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10 TREES OF THE NORTHERN UNITED STATES 
Trees having multiple roots are readily transplanted, 
even when large. The Maples and Elms are of this class. 
Roots that grow from the root-end of the embryo of 
the seed are called primary roots; those growing from 
slips or from stems anywhere are secondary roots. 
Some trees grow luxuriantly with only secondary roots ; 
such trees can readily be raised from stems placed in the 
ground. The Willows and Poplars are good examples 
of this group. Other trees need all the strength that 
primary roots can give them; these have to be raised 
from seed. Peach-trees are specially good examples, 
but practically most trees are best raised from seed. 
A few trees can be easily raised from root-cuttings or 
from suckers which grow up from roots. The Ailanthus, 
or “Tree of Heaven,” is best raised in this way. Of this 
tree there are three kinds, two of which have disagree- 
able odors when in bloom, but the other is nearly odor- 
less. By using the roots or the suckers of the third kind, 
only those which would be pleasant to have in a neighbor- 
hood would be obtained. One of the large cities of the 
United States has in its streets thousands of the most, 
displeasing of these varieties and but few of the right 
sort, all because the nurseryman who originally supplied 
the city used root-cuttings from the disagreeable kind. 
If such trees were raised from the seed, only about one 
third would be desirable, and their character could be 
determined only when they had reached such a size as to 
produce fruit, when it would be too late to transplant 
them. Fruit-trees, when raised from the seed, have to be 
grafted with the desired variety in order to secure good 
fruit when they reach the bearing age. 
