70 Vew- Trees of Great Britain and Ireland 



down the neighbouring trees, the annual rings on 

 the lower parts of the stems suddenly become much 

 broader ; no such stipulation of the increment occurs 

 in the upper part.' 



Frosts are sometimes very injurious. Du Hamel 

 du Monceau^ says that yews suffered in France 

 much damage from the frosts of 1709, and Males- 

 herbes found several killed by the severe frost of 

 1789. 



Galls affecting the growth of Yews. — Selby states 

 that yews are remarkably free from the attacks of 

 insects ; " but next to wind and snow one of the 

 most injurious agents in certain localities is a 

 species of gall {Cecidomya taxi). 



Loudon says : ^ ' Both the wood and leaves being 

 poisonous, neither are attacked by insects, or, if 

 they are, it is in a very slight degree. The points 

 of the shoots, in some situations and seasons, pro- 

 duce little tufts of leaves, which may be considered 

 as abortive shoots.' 



These abortive shoots are due to the insertion 

 of the eggs of a gall-fly (Cecidomya taxi, Inchbald) 

 at the extreme tip of the young shoot, causing an 

 arrest in the growth of the shoot, the leaves being 

 developed in the form of a cone. In this cone the 

 number of leaves amounts from fifty to seventy, or 

 exactly what would have been produced had the 



^ Pp. 26, 302. - British Forest Trees, p. 384. 



^ Arb. and Fr tit. Brit., vol. iv. p. 2091. 



