100 



LEAF ARRANGEMENT AND MOVEMENTS 



web, so that any suitable stimulus or excitant which acts on 

 one part of the organ will soon affect the whole organ. 



117. Vertically placed leaves. Many leaves, like those of 

 the olive (Fig. Ill), always keep their principal surfaces nearly 



FIG. 110. Leaves standing nearly vertical in compass plant (Silphium 

 laciniatum) 



A, view from east or west ; B, from north or south. After Kerner 



vertical. Thus they receive the morning and evening sun upon 

 their faces, and the noonday sun (which is so intense as to 

 injure them when received full on the surface) upon their edges. 



