4 BRITISH OAK GALLS. 



row of punctures in the veins of young and tender 

 leaves in May or June. The marks are very distinct, 

 and the eggs may be easily detected in the tissue of 

 the leaf, but no change takes place until the larva 

 hatches late in August, or early in September ; then 

 the galls of Biorhiza reyium quickly develop. 



Since oak gall formation does not begin until the 

 larva hatches, it is certain that the influence of the 

 larva is necessary, not only for the early stage of 

 development, but also for its completion. Rapid cell- 

 multiplication results from the irritation caused by the 

 larva feeding, and very soon the gall acquires a vascular 

 system of its own, and becomes a more or less indepen- 

 dent structure. 



The cells nearest the larva are very rich in starch 

 granules, while those of the exterior contain tannin, or 

 colouring pigments, or become transformed into hair- 

 lets, papillae, etc. 



In every case, except one, on the death of the larva 

 cell-multiplication ceases. Growth also ceases if the 

 gall be removed from its place of attachment before it 

 has reached a certain stage. It will also die, sooner or 

 later, if the twig or leaf it is upon is severed from the 

 tree. The larva will then either perish, or, if possible, 

 pupate ; the resulting imago, however, is almost always 

 poor and undersized. 



But many of the autumn galls, especially the Nenro- 

 teri, fall from the leaf, and also with the leaf while 

 attached, so soon as the frosts commence, and pro- 

 viding the galls lie in moist situations, slow expansion 

 continues, accelerated by the returning warmth of 

 spring, until pupation takes place ; then growth finally 

 ends. 



The exception to the rule, that gall growth ceases 

 with either the death of the larva or its pupation, is 

 presented in English galls by Andrievs iiiflatov. This 

 gall develops from a bud. It is largely composed 

 of fibro-vascular tissue, and forms an enormously 

 thickened and shortened shoot, with a central longi- 



