THE NUMERICAL ASPECT OF OAK GALLS. 25 
The other correspondent writes: ‘Several workers 
in the West Riding of Yorkshire have noticed that the 
oak trees which are much attacked by Aphilothrix 
fecundatriv usually produce acorns having pink cotyle- 
dons. So pink are they that the colour shows through 
the seed covers. Of course this may be only a coinci- 
dence, but several of us have observed it for some years ” 
(In lit., W. P. Winter, Moorhead, Shipley, December 
29th, 1907). 
