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 Tenthredinidae are comprised 
in the five genera Blennocampa , Cryptocampus , Micronematus, 
Pontania, and Selandria. 
Blennocampa and Micronematus each contain but a single 
representative, and there are only two species of Selandria. 
Blennocampa 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 5 . analis gives rise to pustules on the lobes of the 
Male Fern. The genera Cryptocampus (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 ( Cryptocampus saliceti and C. ater). 
Stem Galls 
(a) Unilateral oblong swelling, 8 to 20 mm. long ( Crypto¬ 
campus ater). 
* “ Enemies of the Rose,” pp. 51, 52 (1910). 
