A 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 renwm quickly develop. 
Since oak gall formation does not begin until the 
larva hatches, it is certain that the influence of the 
larva ig 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, papillee, 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 Newro- 
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 Andvricus inflator. 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- 
