106 BRITISH OAK GALLS. 



bushes and young trees in woods are sometimes badly 

 attacked. Fully developed trees do not*' often bear 

 galls. 



Towards the end of September, or early in October, 

 the parent Cynips emerges from a gall of the year, 

 and at once seeks leaf buds in which to oviposit. She 

 appears to prefer buds on slender and delicate twigs, 

 but occasionally pierces those on the sides of larger 

 branches. As soon as the egg is deposited, growth 

 and development begin. A blastem forms around the 

 egg and the larva hatches. A small and inconspicuous 

 swelling is then formed on the twig. Very slight 

 increase takes place until the following April or May. 

 The embryo gall then becomes more readily noticeable, 

 and l)y the end of June it will have attained the size 

 of an ordinary pea, l)right green in colour if exposed 

 to the light, but golden yellow if in deep shade. 

 Many specimens are also spotted, or streaked with 

 crimson. Until the gall attains several millimetres in 

 diameter, the tissues are enclosed within an epidermis 

 which contains a reddish sap. Few or mau}^ one-cell 

 hairs are scattered over its surface. 



During July larva and gall rapidly enlarge ; the 

 epidermis, not keeping pace with the increase, splits 

 into numerous small scales which quickly fall oft" 

 leaving the surface a beautiful apple-green colour. 

 Early in August considerable internal changes take 

 place, the principal being that the primary nutritive 

 tissue disappears, and oil globules and several pro- 

 teids form the food of the occupant of the cell, the 

 walls of which harden considerably. Little change 

 is then noticeable except in coloration, until the 

 latter part of September. The structure has then 

 become firm and hard. It has attained maturity, 

 and assumed a brownish -yellow or reddish-brown 

 hue. It is firmly attached to the seat of growth, 

 and will maintain its position for two, three, or 

 more, years, neither wind, rain, hail, nor frost, dis- 

 lodofingf it. 



