194 THE GROWTH OF ROOTS AND STEMS. 



62. What functions other than the absorption of water do roots 

 perform ? Illustrate your answer by descriptions of any examples you 

 may select. 



63. Place beneath a bean seedling, fixed as in Fig. 15, a plate pierced 

 by a hole big enough to give easy passage to the radicle. Place the 

 hole so that it does not come immediately beneath the tip of the 

 radicle. How can you cause the radicle (without touching it) to pass 

 through the hole ? 



64. How can you induce radicles to grow upwards instead of down- 

 ivards? How can you induce radicles to leave the earth and enter 

 the air ? How can you get radicles with dense or with sparse root- 

 hairs at pleasure ? 



