226 FUNDAMENTALS OF AGRICULTURE. 



Less common are earth discharges, which occur when 

 the electrical conditions of the clouds and the earth 

 change their potential from negative to positive, the 

 lightning stroke passing from the ground up through 

 the trunk of the tree and its limbs, discharging at the 

 apices of the leaves. 



EXERCISE. Try to find some trees that have been injured by gas 

 or electricity. Do these trees appear as described in this text ? Make 

 a list of the trees on- one of your principal streets that have tele- 

 phone or telegraph wires attached or running through their branches. 

 How would you remedy this condition? 



SECTION XXXIII. ORNAMENTAL TREES AND 

 SHRUBS. 



By PROF. CHARLES A. KEFFER, 

 Department of Horticulture and Forestry, University of Tennessee. 



Adaptability is Important. In every section of the 

 country one may find trees and shrubs especially 

 adapted to the soil and climate, and these have always 

 the beauty of health and vigor. The amateur gar- 

 dener, in his desire for variety and rarity, is apt to 

 search the catalogues for foreign plants, without re- 

 gard to the locality whence they come. People of the 

 plains, seeing beautiful pictures of rhododendron and 

 leucothoe (low evergreen shrub), determine to buy 

 them for their gardens. Their home is in the moun- 

 tains where the air is cool and fogs are frequent, and 

 when transplanted to the plains they become sickly and 

 seldom make vigorous plants. So it is unwise to trans- 

 fer natives of swamps and wet soils generally to dry 

 locations, or in any way to change seriously the natural 

 conditions of soil arid climate to which a plant is ac- 

 customed. 



Select Local Hardy Forms. Fortunately, the more 

 common trees and shrubs used in ornamental planting 

 succeed under a wide range of conditions. They have 

 become common largely through their hardiness and 



