78 



The Root 



out near the surface. It is because 

 of these shallow roots that the fir 

 is able to grow among rocks on 

 the mountain side where there is 

 not much depth of soil to be found. 

 In planting a wood of mixed 

 trees it is well to remember that 

 some have deep roots and others 

 shallow ones, and that as the two 

 kinds exhaust different layers of 

 soil they can be planted together 

 more closely than they could be if 

 this were not the case. Again if 

 trees are to be planted along the 

 edges of a field, deep rooted trees 

 like the oak and elm are better 

 than the often seen poplar, as the 

 latter's roots spread out near the 

 top of the field and hence use up 

 the very soil that will be needed 

 by the crops. The extreme ex- 

 ample of these shallow roots are 

 those of the ash which grow so 

 close to the surface that hardly 

 anything will grow under an ash 

 tree. People used to think that 

 this was because the ash poisoned 

 the ground, but the only reason 

 really is that its roots have used 

 Fig. 39. Wheat seedling, up all the goodness in the upper 



Monocotyledons have a l a y er o f SO J1 go tnat ot h er pl ants 



number of roots of equal , 



size and importance in- starve - 



stead of a tap root. The second way in which the 



