66 



ROOTS 



nutrient solution. If certain ingredients are left out of this 

 solution, the plants placed in it will not live. 



/ "3 T 2 3 



Effect of the lack of certain chemical elements on the growth of plants. The 

 three bottles contain (l) distilled water, (2) all the nutrients, (3) all the nu- 

 trients except potassium nitrate. The second half, B, shows the same seedlings 

 one week later than A. Add other bottles omitting in turn calcium sulphate, 

 calcium phosphate, magnesium sulphate, sodium chloride, iron. Why the 

 difference in amount of growth ? 



Root System. — If you dig up a young bean seedling and care- 

 fully wash the dirt from the roots, you will see that a long root is 

 developed as a continuation of the hypocotyl. This root is called 

 the primary root. Other smaller roots which grow from the pri- 

 mary root are called secondary, and 

 the roots growing from the latter 

 are called tertiary roots. Evidently 

 the root acts as an anchor for 

 the plant, but does it have other 

 uses? 



Downward Growth of Root. In« 

 fluence of Gravity. — Most of the 

 roots examined take a more or less 

 downward direction. We are all 

 familiar with the fact that the force 

 we call gravity influences life upon 

 this earth to a great degree. Does 

 gravity act on the growing root? 

 This question may be answered 



A root system, showmg primary, / , '^ 



secondary, and tertiary roots. by a simple experiment. 



