ADJUSTMENT OF REPRODUCTION 115 



(Fig. 25). If the pot is turned so as to face them away 

 from the light, the leaves will in a short time grow 

 around to face it again. Everyone is somewhat familiar 

 with this fact out of doors. The leaves of the ivy on the 

 wall are all faced out and arranged like a mosaic so as 

 to shade one another as little as possible. The leaves 

 of small plants like the plantain or dandelion spread out 

 in a rosette, facing upward to the light. It is less easy 

 to observe the leaves on trees because one is rarely in a 



Fig. 25. — These plants were grown in a pot placed near a window 

 in an otherwise darkened room. It will be noted that they have 

 grown in a direction which is somewhat of a compromise between the 

 position which they would have taken in response to the stimulus 

 of gravity alone (i.e. if they had been equally lighted on all sides) 

 and that which they would take if influenced by the direction of the 

 light from one side only. 



position to see them from the direction of the incident 

 light, but when he is so situated it will be seen that the 

 leaves do face the light. 



Adjustment of Reproduction. — This sort of adjust- 

 ment is not so obvious to casual inspection, but it is 

 nevertheless vitally necessary. Trees which produce 

 flowers in winter, as they occasionally do, have small 



