224 



STRUCTURE AND VITAL PROCESSES OF PLANTS 



B. The Work of the Root and its Detailed Structure. 



1. Roots as a Means of keeping the upper 

 Structure in Position. 



{a) Find some healthy plants of about the same size, and 

 cut the main roots of them about half an inch below the surface 

 without disturbing the side-roots. It will be necessary to support 

 the stems now by tying them to a stick thrust into the ground 

 beside them. This shows that the main root is best suited to 

 anchor the plant hrmly. Trees having shallow, spreading roots 

 and no distinct tap-roots are easier uprooted than those with a 

 straight deep root. In proportion as the upper structure of a 

 plant grows, it is exposed to the wind, and the more a plant is 



Fig. 207. — Plaiik-ruots ul' tlic Goldnioliur tree {l*uiucia)ia reyia). 



exposed to the force of tlic wind, the hrmcr it must be rooted in 

 the soil. 



(b) But side-roots have their uses as strengthening supports 

 as well, and may be compared to the ropes of a flagstaff that 

 have to keep the flag pole in position. Tlie way in which huge 



