86 EXPERIMENTS WITH PLANTS 



of the Horse-bean, Lima Bean, Buckeye, or the roots 

 of an Onion bulb are best for this experiment. In 

 what region is the most rapid growth ? How long 

 does it continue in this particular place? To what 

 region does it then move? 



When the root forces its way into the soil so ener- 

 getically, what protects the delicate tip from injury? 

 Notice the protective cap which covers the end of the 

 root. Roots of Wandering Jew grown in water (Fig. 

 85), caulicles of Sunflower, Squash, etc., show this 

 cap well. Can you find it in other plants ? Use a lens 

 if necessary. Why is the tip the most tender and 

 delicate part of the root ? Why can it not be strength- 

 ened by tough woody fiber ? Would such fiber prevent 

 growth ? Would it be an advantage to locate the 

 growing region elsewhere than at the tip ? What 

 would happen to the side roots and root-hairs (which 

 are firmly fastened in the soil) if the growing region 

 were above, instead of below, them ? 



What happens if the tip is injured ? Remove the 

 tips from tap-roots growing in water; do new roots 

 appear ? Where do they arise ? In what direction do 

 they grow ? What advantage in this peculiar direction 

 of growth ? 



