DISPERSAL AND GERMINATION OF SEEDS 181 



chors the seedling and establishes a grip on the soil that is 

 necessary for the next events. 



114. Escape of cotyledons and plumule. After the root 

 with its branches has anchored the seedling in the soil, the 

 hypocotyl continues to elongate rapidly. Since it is anchored 



FTG. 149. Seedling of castor-bean, showing the large and green cotyledons. 



now at both ends, one end in the seed and the other in tha 

 soil, elongation expresses itself in the development of an arch, 

 the hypocotyl arch, which may be observed very easily in ger- 

 minating beans (Fig. 146). The bent hypocotyl is in a state 

 of tension, like a bent spring, ready to straighten as soon as 

 it becomes free. This develops a pull on the cotyledons and 

 plumule within the seed, and upon the roots in the soiL The 

 13 



