What is a Vegetable Gall? 3 



1776-96, "Withering British Plants" (ed. 3), ii., 388, it is 

 stated that " the balls or galls upon the leaves are occasioned 

 by a small insect with four wings." Tennyson, in 1842, speaks 

 of a gall, " Talking Oak," 70 : 



I swear (and else may insects prick 

 Each leaf into a gall). 



Most of these quotations without doubt refer to the oak- 

 apple {Terns tenninalis). Probably only a very few of the 

 other oak-galls were known prior to 1840. But for some years 

 previous to that date the excrescences on other trees and 

 plants had been noticed, and the word gall was brought into 

 general use by English naturalists. 



The early writers on the subject of gall-growths appear not 

 to have been able to determine how galls were produced, but 

 were greatly puzzled to account for the ova and the larvae which 

 they found within the tissues of the plant. It was supposed 

 that the ova were deposited by the parent insect in the ground, 

 and from thence drawn up with the sap and carried throughout 

 the tree, until, having reached a certain point, the course was 

 arrested, and the formation of gall-structure commenced. It 

 was also considered possible that the larva, when newly hatched, 

 ate through the cuticle of the leaf, and waited until the sap 

 flowing from the wound enveloped it. Pliny (" Nat. Hist." 

 xvi. 9, 10) was aware that flies emerged from gall-growths ; 

 but, instead of associating the latter with the former, he 

 thought that galls were of fungoid origin and grew as 

 rapidly. J. Rennie ("Insect Architecture," vol. ii., p. 116) 

 was aware "that the mother gall-fly makes a hole in the 

 plant for the purpose of depositing her eggs," and also that 

 "she is furnished with an admirable ovipositor for that express 

 purpose " ; but he does not appear to have penetrated the 

 mystery which then surrounded the development of their 

 growth, for he proceeds to quote from " our older naturalists," 

 that the parent fly "ejects into the cavity a drop of her 

 corroding liquor, and immediately lays an egg or more there ; 

 the circulation of the sap being thus interrupted, and thrown, 

 by the poison, into a fermentation that burns the contiguous 

 parts, and changes the natural colour. The sap, turned from 

 its proper channel, extravasates and flows round the eggs, 



