PREFACE 
T HE 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 
