THE GALL OAK. 17 



less fatal to the vegetable substance to which they 

 are attached. Accordhip: to Virey, an irritation is 

 produced by the introduction of these insects, that 

 resembles a tumour and inflammation in an animal 

 body. The cellular tissue swells ; the parts, which 

 were naturally long-, become round ; and the flow of 

 lifjuid matter produces a chan2;e of orp:anization, 

 from which results a complete chanp^e in the external 

 form of the organ. In this way is the gall produced. 

 The oak-apple is an excrescence of the same na- 

 ture, though effected by a different species of insect. 

 There are various insects possessing the instinct thus 

 to deposit their eggs, that are furnished with an 

 apparatus of the most curious construction, neces- 

 sary for puncturing the branch, as is done by the 

 parent ; and for piercing a way out of the gall, as is 

 done by the insect produced, after it has passed its 

 larva state. Each species of insect chooses not only 

 the particular vegetable, but the part of that vege- 

 table which is best adapted for the reception of its 

 larvae ; and in this way the same plant, for instance 

 the oak, sometimes receives the nests of twenty dif- 

 ferent species of insects. A gall sometimes contains 

 a single larva, sometimes many, and it is thus either 

 called simple or compound. A late agreeable writer 

 on Natural History has given us some sensible ob- 

 servations on the subject of galls, and the instincts of 

 the little creatures that produce them : — 



" The insect that wounds the leaf of the oak, and 

 occasions the formation of the gall-nut, and those 

 which are likewise the cause of the apple rising on 

 the sprays of the same tree, and those flower-like 

 leaves on the buds, have performed very different 

 operations, either by the instrument that inflicted the 

 wound, or by the injection of some fluid to influ- 

 ence the action of the parts. That extraordinary 

 hairy excrescence on the wild rose, likewise the result 



c 3 



