- 3 2 4 - 



the succeeding table. These diseases I have ranged into several 

 classes: a) severe, and attacking young plants (seed-beds and nur- 

 series, etc.); b) slight, and attacking young plants; c) severe, and 

 attacking older trees; d] slight, and attacking older trees. There 

 is a certain vagueness in the classification because I have had to 

 use my judgement, first, as to whether the disease is severe when 

 it does attack the tree, and secondly, as to whether it is sufficiently 

 common on the tree to be reckoned as a menace; but diseases 

 caused by insects that rarely attack the species I have reckoned 

 as ' slight. ' In order to check my estimate I have drawn up the 

 list of insect foes that attack the same species of forest trees and 

 are admittedly of such importance as to be included in the small 

 work on ' Forest Protection ' by Fiirst ; the results are given in 

 column 8 of the same table. The results of both methods of esti- 

 mating agree in showing the larger number of insects menacing the 

 existence of coniferous species. 



NUMBER OF SPECIES OF INSECTS ATTACKING. 



