12 



or witch grass, and see if all the underground parts of these are roots 

 or if some of them are stems. 



You have all tried to pull plants out of the ground ; and in doing so, 

 you have noticed that some pull up quite easily and others with much 

 difficulty. Pull up, for example, a corn 

 plant or an oat plant and then pull up 

 a burdock or a clover plant. Why is it 

 so much easier to pull up the corn or oat 

 plant than the burdock or clover plant ? 

 If you will dig down into the earth you 

 will see that the clover and burdock 

 plants have a long main root extend- 

 ing deep down into the earth, and that 

 other smaller roots branch off from this 

 at different depths and extend out into 



the earth in all directions, whereas the -^f4^^-:r; -Tj 



'1^>^:. 



oat and corn plants have no such main 

 root, having only the smaller roots ex- ^'^ 

 tending out from the base of the ste 



m. 



'. 10. Showing the tubers arisinjj from the 

 stem and quite distinct from the roots of 

 the potato plant. 



Hence the oat and corn plants are much 



more shallow-rooted than the clover or burdock. If you will pull up a 

 number of plants you will find some like the corn and others like 

 the burdock or clover, some with very deep and others with very 

 shallow roots. This is one of the many reasons why a good farmer 

 grows different crops and not alwavs the same crops, or, as it is called, 

 follows a " rotation of crops " on the same field from year to year. One 

 year he may grow deep-rooted plants, and these will feed upon the food 

 that is deep down in the earth, and the next year he will grow more shallow- 

 rooted plants, which will feed 

 in another part of the soil; and 

 thus the plants are not so likely 

 to use up all the food from any 

 one part of the soil. 



This main root, which vou 

 noticed in the clover or burdock 

 is called the primary root. The 

 smaller roots growing from the 

 primary root are called second- 

 arv roots These in turn mav 

 branch, producing third or 

 tertiary roots, and so on until 

 the whole root system of the 

 plant is formed. When the 



Fig. 11. Showing root system of nrimwrv rnnt iv; vprv miirh laro-pr 

 clover and oats. Note the main root Pilmfl' } rOOl IS \ er\ mucU larger 



of the clover extending deep down into than the Secondary roots, as we 



the soil and the fibrous or more shal- , , , -^11..^ 



low roots of the oat plant. have already seen in the beet, 



carrot, turnip, and dandelion, 

 it is called the tap root. In the case of the corn or oat plant, you will 

 not have noticed any primary roots. As a matter of fact, if you were 



