WOUNDS 269 



development, and some of which may even produce short shoots. 

 The trees are, however, unable to reclothe themselves with a 

 permanent supply of leaves, for the following reasons. During 

 the year in which defoliation takes place, all, or nearly all, the 

 reserve supplies of plant-food that are stored up in the tree are 

 made use of by the cambium in the formation of a wood-ring. 

 No growth takes place in the following year. The reserve 

 supplies in the young shoots also are quickly consumed by the 

 cambium, so that the buds are prevented from forming shoots. 

 In the course of the autumn and winter, especially during 

 long-continued winter drought, all, or nearly all, the twigs and 

 branches of the crown die for want of water. The bole of 

 the tree maintains its vitality till the middle of summer that is 

 to say, for a full year after defoliation. During that period, 

 however, no growth takes place. Then the inner cortex begins 

 to become brown, and the bole dies. This is largely due to 

 the high temperature of the tree, which is induced by the lack of 

 shade in a wood that has been entirely defoliated by the ravages 

 of insects. Especially is this the case with spruces, whose bark 

 is but ill-adapted for mitigating the action of direct insolation. 



Should the defoliation not have been complete, the wood 

 may slowly recover. This is most likely to occur when a 

 mild wet winter follows the season in which the ravages were 

 committed. New shoots are formed on those branches which 

 have retained a large proportion of their leaves, and which have 

 therefore been in a position to produce reserve materials 

 even while the insects were at work, and to store them up 

 for use during the succeeding season. The thin-barked spruce, 

 however, is apt to succumb to bark-scorching, consequent on 

 direct insolation. Trees which are to a certain extent protected 

 against the action of the sun by the foliage of their neighbours 

 may gradually recover, even after having lost a great deal 

 of their foliage, but not after complete defoliation. 



