THE planter's GUIDE. 



93 



before tlieir maturity all the pabulum in their immediate 

 neighbom-hood, will at length be fomid searching for food at 

 a distance from the trunk equal to the height of the trees 

 themselves. At all events we are aware that, even with 

 trees of a youthful age, the roots and branches are co-ex- 

 tensive with each other ; or rather, that superior extent 

 is generally found on the side of the roots. 



In the more confined parts of the forest the reverse of 

 this usually takes place, from the warmth generated by 

 shelter, and from the injurious effects of evaporation being 

 obviated. Here roots, and especially fibres, are of far 

 less extent and strength, and also fewer in number, than 

 in open positions ; and hence the risk arising from thick- 

 ets or close plantations being too suddenly laid open, as 

 above mentioned. The want of a stronger system of root, 

 in such cases, is sufficiently accounted for by the reason- 

 ings already given, and by a sufficient supply of the 

 descending sap. 



In order to enable trees to withstand the wind, there 

 is nothing more important than the tap-root, or root that 

 has its determination directly downwards. Roots and 

 branches, as has been already observed, are relative and 

 correlative; and I am inclined to think that a striking 

 resemblance of character exists between the leading shoots 

 and the tap-roots, insomuch that they will be found not 

 only analogous to, but also co-existent with each other. 

 While the tree continues in full vigour, and has not as yet 

 attained its ultimate height or size, it has a leading slioot 

 or shoots at top ; and at that period we find' that there 

 is, in like manner, underground, a leading tap-root of cor- 

 responding vigour. When the leading shoots of the stem 

 begin to lose their pre-eminence, and gradually disappear 

 among the other branches, the top of the tree assumes a 

 rounded form, and becomes what is called clump-headed. 



