34 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



I say this with deliberation because the old theory, con- 

 tradicted by the operations of coppicing and pollarding, that 

 there is an absolute co-relation between the root-system and 

 the branch-system of a tree in consequence of which the removal 

 of a branch implies the death of the co-related root, appears 

 to have adherents still. The science of the matter is really 

 this: — The roots depend for the elaborated food-material they 

 require for growth upon the area of green assimilating surface 

 exposed by the epigeous portions of the tree to the air ; these, 

 in their turn, depend for water and mineral salts upon the area 

 of absorbing hairs upon the root tips. There is no necessary 

 relation between any definite areas in the two regions above 

 and below ground : the colonial organisation of the plant secures 

 the service of every active cell for the interest of all others. 

 Shoot pruning does not kill roots. The disastrous results that 

 follow over-pruning, and, no less, bad pruning of trees, arise 

 not from death of roots, but from the deficiency of branches 

 d'appel — in our less flexible language "water-lifters" — which 

 are the agents for the efficient distribution of the supply of 

 the water and salts from the intake in the root. Given adequacy 

 in respect of these, all else in the nutritive processes will follow ; 

 for the tree, extravagant though it may appear in its output 

 of branches, which are crowded out and cumber it, is essentially 

 thrifty in accumulating, during opportunity, vast stores of reserve 

 food-material upon which indent is made for repair and the 

 evolution of new shoots, provided the water supply be sufficient. 

 It is the abundance, the healthiness, and the accurate placing 

 of these branches d'appel upon the trees in the Mall that are 

 so significant for the present and future life of the trees. 



4. The pruning of the laterals has encouraged the steady 

 upward growth of the main stem without forking or 

 divarication of the top. The exuberance of apical 

 growth has, however, been wisely kept in check, and 

 a balance between the apical growth and develop- 

 ment of laterals has been thus maintained. I say 

 this with emphasis because this checking of the 

 "leader" has been, I see, specially condemned, and 

 I must endeavour to explain now the reasons which 

 justify the method that has been pursued. 

 I have stated on a previous page that no shoot in the plane 

 tree continues growth by a terminal bud. Its elongation is 



