98 POPULAR EEEOES. 



is used requires to be assimilated during a com- 

 paratively short growing season it is placed near 

 the surface where it will rapidly decompose. It 

 has been shown, however, that the roots of onions 

 are not confined to the surface soil and that the 

 character of the subsoil is by no means unim- 

 portant. But the main reason why shallow culti- 

 vation succeeds so well with the onion is that the 

 roots grow best in a compact soil. If deep plowing 

 is given to improve the subsoil, and then the soil is 

 allowed to settle a few months before the seed is 

 sown, and shallow cultivation afterwards given the 

 best results will be obtained. So the general prac- 

 tice of shallow cultivation for the onion is about 

 right, though the explanation which attributes it to 

 the supposed shallow rooting habit of the plant is 

 erroneous. 



A popular idea in regard to the roots of trees is 

 that they grow outward only as far as the limbs 

 extend. There is often some relation between the 

 spread of the top and the lateral growth of the 

 roots. Pear trees, which are inclined to grow 

 upright, have roots which grow more, directly 

 downward than do the roots of apple trees, the tops 

 of which are more inclined to spread. This rela- 

 tion, however, has been but little studied, and 

 whatever truth there may be in it, it is certain that 

 the roots of all our ordinary trees extend much 



