108 ESSENTIALS OF BOTANY 
the sun without cutting off too much light from other 
leaves underneath. Such a leaf is in much less danger of 
being torn by severe winds than are broader ones with 
undivided margins. The same purposes are served by 
compound leaves with very many small leaflets, such as 
those of the honey-locust, mimosa acacia (Fig. 77), and 
Fic. 74. Opposite Leaves of Deutzia! (from the same shrub as Fig. 75), 
as arranged on a Horizontal Branch. 
other trees and shrubs of the pea family. What kind of 
shade is produced by a horse-chestnut or a maple tree 
compared with that of a honey-locust or an acacia? 
127. Daily Movements of Leaves. Many compound 
leaves have the power of changing the position of their 
leaflets to accommodate themselves to varying conditions 
of light and temperature. Some plants have the power 
of directing the leaves or leaflets edgewise towards the 
sun during the hottest parts of the day, allowing them to 
1 Deutzia crenata. 
