THE PLANT BODY 



39 



cases curvature is due to slow, unequal growth on opposite sides 

 of a part, while in pulvinar movements the curvature is due to 

 rapid temporary growth caused by the unequal inflation with 



FIG. 22. Positions assumed by the leaves and roots 

 of a young plant of red clover in normal light 



a, the entire plant; b, three leaflets with pnlvini 



Pulvinus 

 Petiole 



water of the cells on 

 the upper and lower 

 sides of the pul- 

 vinus. This highly 

 specialized type of 

 leaf movement by 

 pulvini, observed 

 above in the bean 

 and the red clover, 

 is characteristic of 

 the entire pea family 

 (Leguminosae), to 

 which they belong. 

 Alfalfa, the com- 

 mon clovers, locust, 

 peas, beans, and the 

 sensitive plant (Mi- 

 mosa) are other well- 

 known members of 

 this very important 

 family of plants. The 

 contrast between the 

 caladium and the 



clover plants outlined above emphasizes the fact that each plant in 

 any given environment is able to adjust its organs by movements 

 so as to adapt them to surrounding conditions. The amount and 



