List of the Insect Fauna of the Counttj. 105 



before the removal of pressure, as in the case of plant- 

 cuttmgs, the growth of trees, &c. Gall-growth may be 

 similarly affected by the removal of pressure through the 

 puncture made by certain gall-producers, and in obvious 

 other ways. 



Sir James Paget has recently followed up Dr. HolUs's 

 suggestions in enunciating the importance of the comparative 

 pathology of oak-galls, in the remarkable address before 

 quoted. I cannot forbear giving his valuable remarks relative 

 to gall pathology in extenso, with the hope that some of our 

 members may be led to take up this interesting study, which 

 so closely affects both animal and vegetable physiologists. 

 These were his words : — 



*'0f all morbid processes in plants, none, I think, are so 

 suggestive as are those produced by parasites, whether vege- 

 table or animal. The whole subject would be far too large 

 to speak of, even if I were familiar with it ; it is, indeed, a 

 subject of the gravest national importance; but, keeping to 

 the design with which I started, and wdiich was only that of 

 pointing out where useful pathological knowledge may be 

 gained, I will speak of only some of the changes which are 

 produced by insects. The most remarkable of these are the 

 galls ; and, among the many hundreds of them that have 

 been described, I may assume that you know some in their 

 natural mode of growth — such as the common oak-apple, 

 with which some celebrate the restoration of our monarchy ; 

 and the bedeguar of the wild rose ; the bright crimson oak- 

 spangle, the currant-gall, or the artichoke -gall, or the gall of 

 pharmacy. But, besides the hundreds of different true galls, 

 there are still more hundreds of changes of structure in 

 leaves and stems and roots, all produced by the irritant 

 secretions of insects, and all such as may justly be ascribed 

 to processes of inflammation. In some, as in the 'curl' of 

 the leaves of the whitethorn, you find thickenings of leaves 

 which are lifted, rolled, or curled into chambers, which serve 

 for defence of the Aphides or other insects ; ^ in some, the 

 thickened and distorted clusters of leaves, in buds or on 

 twigs, roll up and are mutually fastened, so as to form the 

 walls of similar defensive lodgings; in some cases, leaves 

 become swollen as with a kind of oedema ; in some, their 

 layers separate as if with bhstering ; or leaves, or stems, or 

 fruits,' or clusters of flowers, buds, or roots, produce variously 



