MODE OF INFECTION OF LARCH CANKER. 1 33 



vulnerable tissues, Mr Hiley proposes that the branches should 

 be cut during a spell of dry weather between January and March 

 when the spores of the fungus are not being shed. They are 

 only shed in a damp atmosphere. The experiment certainly 

 seems worth making. In districts where dry spells are not to be 

 depended on, a touch of Archangel tar would presumably protect 

 the wound. Mr Hiley, however, remarks that in Bagley Wood 

 where larches have been used as nurses for other trees and have 

 had their side branches systematically shortened, no canker has 

 appeared though the fungus is frequent on the cut branches on 

 the ground. 



The experiment as outlined by Mr Hiley is as follows : — 

 " When the trees are six to eight years old the lowermost 

 branches are to be cut off, up to and including the oldest living 

 branches, one half inch from the trunks. Each year in a spell 

 of dry weather during the winter a fresh lot of branches is to 

 be cut in such a way that every branch is removed at a time 

 when it would have soon died naturally if left. After each 

 cutting the branches should be collected and burnt so as to 

 reduce the number of fructifications in the neighbourhood. If 

 in bad canker districts foresters would treat plots experimentally, 

 pruning half in the way I have described and treating the rest 

 according to the older method, much evidence might be gained 

 either in support of the theory I have outlined or against it." 



Sir William Schlich has arranged for experiments on these 

 lines in Bagley Wood. 



Mr Hiley's paper seems to afford a possible explanation of the 

 comparative immunity from disease of thinly grown larch woods. 

 Hitherto this immunity has been attributed to the fact that 

 abundance of space favours a vigorous growth in the larch while 

 it tends to deprive the fungus of its favouring conditions. Is it 

 also due to the fact that the side branches remain alive until the 

 section of the stem from which they spring has passed the 

 vulnerable age during which a canker imparted by a decaying 

 side branch is a serious menace to the tree ? 



