GALLS 173 



islands into line with that of the galls of Central Europe 

 and Italy. I also hope to be able to extend our records of 

 the distribution of the gall-makers in our country. I ask the 

 co-operation of all who may observe galls to aid me in this 

 by kindly forwarding to me examples of the various forms, 

 fresh or dried. Each specimen should be labelled with the 

 name of the food-plant (unless the part sent is sufficient to 

 show this), the collector's name, the locality, the approxi- 

 mate height above the sea -level, and the date. I will 

 gladly supply the names of the makers if it is possible to do 

 so. It will make this easier if the sender will number each 

 kind sent, retaining an example bearing the same number. 

 Examples from almost any locality in the country will be 

 welcome, no matter how common they appear to be. So 

 little is recorded as to the distribution that every scrap of 

 information will be helpful. 



Galls form a most interesting subject of study. The 

 power that certain low forms of plants and many animals, 

 belonging to widely different groups, possess of influencing 

 the growth of the cells of their hosts so as to give rise to 

 structures usually of a very definite nature is one that man 

 has not yet been able to acquire, even in a limited degree. 

 The change produced is in most cases so characteristic that 

 the galls can be recognised with as great certainty as, and 

 with far greater ease than, the gall - makers themselves. 

 Indeed, in a good many cases, for example among certain 

 Cynipidtz, the gall-makers can scarcely be distinguished from 

 one another, while the galls are very different. A con- 

 tinuous gradation leads from galls that are little more than 

 a slight enlargement of the part, or a mere surface distortion, 

 to those so highly specialised in form, and of so varied 

 tissues, that they appear like wholly new parts not repre- 

 sented in the normal organs of the plant. 



A clear and accurate conception of the nature of the 

 change induced by the gall-maker in the processes of nutri- 

 tion and of growth characteristic of the healthy cells would 

 be a most valuable contribution to our knowledge of 

 physiology. In the simplest galls, often scarcely deserving 

 the name, this change is probably due to local irritation 

 caused by the parasites absorbing their food from the 



