20 BRITISH GALLS 



ture of the plant profoundly modified. The cells forming 

 the boundary are more regular than those near the centre ; 

 they are also smaller and more elongated, and this outer 

 layer (which may be composed of one, two, or three rows of 

 cells) contains few or no stomata." 



The British gall-causing Tenthiedinidae are comprised 

 in the five genera BUnnocampa, Crypiocampus, Micronematus, 

 Pontania, and Selandria. 



Bhnnocampa and Micronematus each contain but a single 

 representative, and there are only two species of Selandria. 

 Bhnnocampa pusilla attacks the leaves of wild and cultivated 

 Roses, causing the margin to roll upwards. Theobald 

 remarks concerning this gall :* " If one of the folds is 

 opened we find inside one or more pale greyish-green or 

 grey larvae. This folding of the leaves is mainly accom- 

 plished by the larvae, and as far as I can see it is done by 

 them when immature. Cameron, however, says that they 

 are aided by the incisions made by the females when they 

 lay their eggs. The deformity produced in the leaves 

 varies, but the rolls are always more or less cylindrical. 

 When the leaf dies, the larvae move to another." Microne- 

 matus abbreviatus causes pustular growths on Pear leaves. 

 Selandria temporalis causes the pinnules of the Bracken to 

 swell, and S. analis gives rise to pustules on the lobes of the 

 Male Fern. The genera Crypiocampus (Euura) and Pontania 

 (Nematus) contain several species causing galls on Willows. 

 For the purpose of assisting identification of the galls they 

 may be arranged as follows : 



Bud Galls 



The greatly swollen bud does not open, and eventually 

 dries up {Crypiocampus saliceti and C. ater). 



Stem Galls 



{a) Unilateral oblong swelling, 8 to 20 mm. long {Crypio- 

 campus ater), 



* " Enemies of the Rose," pp. 51, 52 (1910), 



