THE FUNCTIONS OF A LOCAL NATURAL HISTORY SOCIETY. 23 
Having described at length the general aims of a local society, 
I will now turn to a special instance of the work which should be 
undertaken by the members. As an example, I will take a 
subject which has been greatly neglected both in England and 
abroad, but especially in England; and which, therefore, offers 
the certainty of fresh discoveries, interesting to naturalists 
generally, and which, in addition, requires that botanists and 
entomologists should both co-operate. This subject is the col- 
lection of Plant Galls, a record of the species of plants on which 
they occur, and the determination of the creatures which give rise 
to their formation, and which feed on them. When once formed, 
the galls serve as food, not only to the gall-producer, but also to 
other insects which are called Inquilines. I do not suppose that 
a tithe of the different kinds of galls to be found in Great Britain 
have yet been described. In Kaltenboch’s ‘“‘ Pflanzenfeinde,” 
published fifteen years ago, more species of Cynipidee are named 
as producing galls on the oak alone, than all the number of 
species of that family yet recorded in Great Britain as causing 
galls on all our seventeen hundred and odd species of flowering 
plants. 
Now what is a Plant Gall? Vegetable galls are excrescences or 
deformities of living plants, caused by animal influence, and 
serving for the protection and sustenance of animal brood. ‘Their 
formation always takes place while the plant is still growing, but 
their functions do not always cease with the decay of the plant, 
the juices of which helped to form them. It happens in many 
instances that the ripe gall becomes detached, and continues to 
afford shelter and food to its inhabitants; this is particularly the case 
with the galls originally formed on the organs of deciduous trees or 
low plants of annual growth. Very few families of plants are 
altogether free from these parasitic growths, but I believe that none 
have yet been detected on mosses and fungi. Galls occur on all 
vegetable organs—root, stem, branch, bud, leaf, blossom, fruit, 
all are liable to be injured in this way, and to have their own 
sap diverted to the support of another organism. A gall is, 
_ therefore, an excrescence or swelling on some part of a plant, 
