SHADE TREES. 155 



or number of hours of sunshine are correlated with growth and develop- 

 ment of vegetation, although temperature is very important too. 



Morning light is more intense that that of the afternoon, and this 

 difference exerts an influence upon the growth of trees. Measurements 

 of a large number of tree stumps ranging from ninety-five to two hundred 

 and twenty years old showed 17 per cent, more growth of the radii on the 

 east side than on the west, and the radii measurements attained from the 

 stumps of a row of ash trees running north and south were 24 per cent, 

 greater on the east than west side. Two rows of trees bordering either 

 side of a road running approximately east and west showed a difference 

 of 11 per cent, in their circumference growth 4 feet from the ground, 

 during a period of seven or eight years, in favor of the south row. Daily 

 measurements of light made by us for one year showed an average dif- 

 ference of 10 per cent, in favor of morning conditions. Since photosyn- 

 thesis or carbon assimilation is proportionate to light intensity, and 

 growth is in proportion to photosynthesis, there naturally follows a 

 greater growth on the east than on the west sides of trees, and the 

 same holds true for the east and west slopes of high elevation. The light 

 conditions at high elevations are more intense than low elevations, and 

 the difference may equal 25 per cent, more or less, depending upon the 

 altitude and other conditions. 



Light is an important factor in the process of photosynthesis or carbon 

 assimilation in leaves, about 95 per cent, of the structural material of the 

 tree being obtained by tliis process. Light inhibits growth and stimulates 

 the formation of mechanical and resistant tissue; on the other hand, 

 darkness or lack of light stimulates growth. Light affects the size, color 

 and texture of the foliage, and, in fact, the whole configuration of the 

 organism. 



Since morning light conditions are better than those in the afternoon 

 iJt is well to set trees with their poorest developed sides towards the south- 

 east, as they will become more favorably exposed to light conditions; 

 hence they will develop more rapidly on this side. Moreover, an avenue 

 of trees located on the east and south sides of a road will develop more 

 rapidly than those on the west and north sides, and trees and crops located 

 on the east side of a hill will develop more rapidly than those located on 

 the west side. An east exposure is therefore much better for the rapid 

 development of an orchard than a west exposure, and the same holds 

 true for different crops and shade trees. 



Transplanting. 



Too little attention is given to the details of transplanting. It is quite 

 essential that soil conditions should be suitable for the growth of the 

 particular species of tree planted, and in the selection of material for 

 planting there is great need of more care. A lai'ge amount of poor material 

 is constantly being used, besides wliich, injudicious use of the knife and 

 pruning shears maims many trees for life. Trees 6 to 8 feet high are usually 



