Seasonal Notes — October 269 



leaves normally, whilst its neighbour retains them through- 

 out the winter, though, of course, in a withered state. This 

 phenomenon was briefly alluded to in our first number, accom- 

 panied by a plate ; it is the more frequently observed in 

 young oaks and very young beeches. We know of one birch 

 which also exhibits this peculiarity. 



The Influence of Galls upon the Colour of Leaves. 



If we go into a beech coppice and look carefully at the 

 leaves covering the ground we shall observe that the majority 

 are quite brown, but here and there will be seen a leaf with 

 peculiar little bright green patches upon it. Picking it up, 

 we shall find in the centre of each patch a hairy gall looking 

 like a little cocoon about an eighth of an inch long, standing 

 on its end. It is, in fact, a vegetable cocoon, the home of the 

 larva of a small fly, Hmnomyia peligeva. The creature did not 

 construct its own home, it was obligingly made for it by the 

 plant. The deposition of the egg by the parent fly within 

 the tissues of the leaf caused irritation of the cells around 

 it, consequently there was greater attraction of sap to that 

 part, with the natural sequence, abnormal growth. 



But not all our green patches will bear the galls, in some 

 cases they will have fallen away, but the scars of detachment 

 will be readily seen. In others serpentine burrows occur 

 instead of galls, the work of leaf-mining grubs. In not a 

 few the larva may be found within. 



Exactly the same phenomenon may occasionally be seen 

 in oak leaves ; the leaf for the most part being withered 

 and brown, but here and there retaining bright chlorophyll 

 patches. On the lower surface we find the centre of each 

 oasis occupied with the capped spangle gall (Neuroterus 

 fumipennis) alluded to on p. 221 of our last issue. Oak 

 leaves, with the galls of Neuroterus lenticularis , the common 

 Spangle Gall, on the under surface, usually show brown spots 

 on the upper side early in autumn. Apparently the presence 



