PREFACE 



THE principal facts as regards the galls which are 

 developed on plants and trees, and which present 

 such various forms, have long been recognized, since 

 they are, for the most part, very conspicuous. It is, 

 however, only recently that they have become the 

 objects of special study, and there is yet much con- 

 cerning them which needs further investigation. 



Although during quite recent years much has been 

 written respecting them and several valuable works 

 have been published, chiefly on the Continent, a text- 

 book with a classified descriptive catalogue of British 

 galls was needed, and will be welcomed. The prepara- 

 tion of it, I feel sure, could not have fallen into better 

 hands than those of Mr. E. W. Swanton. It demands 

 a knowledge both of plant life and that of insects. Of 

 both of these Mr. Swanton possesses, I know, a sound 

 and extensive knowledge. His little treatise on Fungi 

 is well known and widely read. 



It is not long since the writers on insect galls, almost 

 without exception, were in the habit of speaking of 

 them as if they were made by the insects; and although 

 it. is now generally recognized that they are the results 

 of a sort of partnership between animal and vegetable 

 life, the shares taken by the two forces are by no means 



