Galls affecting Groivth 73 



the only healthy shoots remaining being formed as 

 a dense spray on the upper surface of the main 

 branches. The ground under the tree was here 

 and there covered with the little rosettes or cones 

 which had been bitten off by birds (probably tit- 

 mice), in every instance the larva having been 

 extracted. 



At Binder, near Wells, I saw, some years ago, a 

 number of trees about 15 feet high and 3 feet in 

 girth at the base, planted about sixty years ago, all 

 much infested by Cecidomya on their upper branches, 

 which were stunted and unhealthy-looking, while 

 the lower branches, which were almost free from 

 galls, were well-grown and vigorous. The whole 

 tree showed one of the marked effects of pollarding, 

 viz., rapid growth of the lower trunk and branches. 



If we examine into the results following injuries 

 of the main stem, or more important branches, 

 produced by the causes above mentioned, we find 

 that all the remaining part of the trunk or branch 

 below the site of injury generally dies at once, with 

 exception of its coverings, the bark and its under- 

 lying liber and cambium layers. These latter 

 begin to form a new ring of wood enclosing the 

 old dead trunk, creeping over and covering up cut 

 or broken surfaces. This process has been likened, 

 with a good deal of force, to the necrosion of a 

 shaft of a bone, and its inclusion in a new bony 

 case produced by the periosteum. The simile is in 



