108 MISSOURI BOTANICAL GARDEN BULLETIN 
vere the pruning the more compact is the top with an abun- 
dance of shoots close to the stem. The roots require no 
pruning except where bruised or broken. 
In this first operation there is no difference in treatment 
between the lawn and street tree. In later treatment the 
lawn tree is allowed to grow at will and to assume its nat- 
ural form, requiring but little attention except the careful 
removal of dying limbs. On the other hand, the street tree 
must be straight and symmetrical, with branches beginning 
at a height sufficient to permit free passage underneath. 
These essentials are secured through the medium of pruning. 
The lower branches should be allowed to remain until the 
trunk thickens enough to support the top, their removal 
then being accomplished in yearly intervals until a height 
of 10-12 feet is reached. 
The training of the crown consists of the suppression of 
some branches and the encouragement of others to produce 
a compact and symmetrical me i A single leader is de- 
sirable in order to eliminate the danger of the formation of 
crotches with their tendency to split. Strength may be 
thrown into the central stem either by the removal or short- 
ening of co-leaders. In cases where tops bend over and 
droop the leader may be tied with raffia to poles and thus 
forced to remain upright until strong enough to need no 
support. The loss of a leader may be replaced by training 
a lateral twig to take its place. All dead and imperfect limbs 
should be removed. If the top becomes so dense as to exclude 
the sun from the sidewalk or near-by buildings it should 
be thinned by removing the third or fourth division of 
branching, but not the main laterals. In eliminating the low- 
er branches the main laterals need not be removed to any 
great height, the subdivisions being cut so as to produce a 
graceful upward sweep. 
It is essential to bear in mind that the natural shape and 
habit of the tree should be preserved and all artificia shap- 
ing avoided. The retaining of the natural form involves 
considerable skill which is often obviousl lacking in the 
treatment of many of our street trees. hey should not, 
however, be permitted to Pies beyond certain bounds, their 
spread being restricted when too much shade is cast. upon 
the roadway or adjoining houses. Shortening of branches 
Is necessary to produce compactness of form. Since the root 
system usually has the same diameter as the top, and as the 
poor street soil generally restricts the growth of the roots, 
the spread of the top should be limited in roportion. The 
necessity for cutting back is manifested i the branches 
becoming ragged toward the top and the foliage thin. 
