FUEE CHOP OF UNIFOEM AGE. 



21 



pressure from its more powerM neighbours, and can thus draw its 

 nourishment from within a smaller area of ground. The richer and 

 moister the soil is, the more Kmited will be the area from which a 

 given plant can obtain all the nourishment it requires, and hence 

 the less tendency will the plant have to spread out its roots, and, for 

 one and the same density of the crop, the less intense will be the 

 struggle for existence. 



The depth to which the roots of any species can penetrate depend* 

 on the depth and stiffness of the soil and the character of the sub- 

 soil. When downward extension is limited by a shallow or stiff soil 

 and an impenetrable subsoil, the plants compensate themselves by 

 spreading out their roots laterally. Generally speaking, for indivi- 

 duals of one and the same species, depth and narrowness of crown 

 bespeak deep rooting, while breadth of crown without much depth 

 means a lateral spread of roots. Hence the shallower and stiffer the 

 soil and the more impenetrable the subsoil is, the severer will be the 

 struggle for existence and the earlier will it be decided. 



But whatever the system of root-development peculiar to any spe- 

 cies may be, for several years at first, the number of years varying 

 with the species, the seedling consists of only a single main root and a 

 small crown composed of a few leaves and hardly any or no branches. 

 During this phase of development the young plant can do nothing 

 more than merely push down this main root beyond the reach of 

 ordinary drought, being unable to absorb and, therefore, also to 

 elaborate more nourishment than what suffices for this purpose. In 

 this way the taproot gradually elongates and strengthens itself by 

 throwing out a few small branches until, having taken a sufficient 

 hold of the soil, it is able at once to meet a much larger demand 

 from the crovra above, which itself also has in the meantime been 

 growing fuller and stronger. This is the meaning of the phrase 

 of " a plant establishing itself" and a seedling at this stage is said 

 be established. The seedUng is now able to make a rapid start up- 

 wards, and the roots, better nourished than before by the very much 

 stronger and constantly expanding crown, take a vigorous lateral 

 extension. 



With stool-shoots and root-suckers it is otherwise ; their roots are, 

 for a time at least, the roots of the parent tree itself. In the case 

 of stool-shoots most of these roots soon die, since the shoots cannot 

 obviously elaborate enough nourishment for them ; so that a great 

 abundance at the outset is followed by a rapid shrinkage, and this 

 in turn by a gradual expansion as the shoots continue to develop 

 their own roots, the rapidity of expansion being directly proportional 



