TEXTBOOK OF LANDSCAPE GARDENING 
8. How many trees show burning or similar injury from electric 
wires? 
9. How many trees show gas poison? (It may be necessary 
to read up on the symptoms of this disease.) 
10. List any other defects. 
It will probably be found that a vary large percentage of street 
trees are defective in one way or another. In fact there are many 
sections where hardly a perfect tree can be found. When the re- 
ports of all members of the class are brought together and summar- 
ized they should show the number of instances of ice damage, horse 
damage, gas, poison, electric line injury, etc. This will indicate 
pretty clearly what causes pull down the average health of trees, 
and thus suggest where effort should be directed toward improving 
conditions. 
Other matters which may be investigated if there is time are 
drainage, irrigation, fertilization, spraying and laws for the pro- 
tection of trees. 
References 
SoLoTAROFF, Shade-trees in Towns and Cities, New York, 1911. 
Peets, Practical Tree Repair, New York, 1916. 
Mutrorp, Planting and Care of Street Trees, U.S. Dept. Agr., Far- 
mers’ Bul. 1209, Aug. 1921. 
84 
