IV 



BOTANICAL CHARACTERISTICS 45 



stalk (Fig. 7). These articulations enable the leaves 

 to make movements in different directions, in order 

 that their upper sides may always be turned towards 

 the side from w r here the strongest light comes. A 

 simple experiment shows this clearly. If a cocoa 

 plant is placed in a box closed on all sides except one, 

 which is facing the light, after six to twelve hours all 



F IG . g. Flowers on the stem of a cocoa tree. 

 The flowers all arise from the same " cushion." 



the leaves will have turned with their upper sides 

 facing the light. This influence exerted by the rays 

 of light is called heliotropism. 



A further characteristic of the just unfolded leaf 

 is the presence of two small leaflets near the base of 

 the leaf-stalk. These leaflets, called stipules, fall off 

 very soon, generally even before the leaf is full- 

 grown. It is questionable if these stipules are of 

 any use to the plant; it may be, however, that 

 they protect the bud against the rays of the sun or 



