GALLS INDUCED BY PLANT-LICE 85 
and within the roll her numerous progeny go through 
their moults. The adults fly to other trees, and there 
deposit their remarkable progeny. Buckton* observes: 
“ These young are born in the form of yellow ova, and 
might be almost mistaken for such, except from the existence 
of two black eyes which are sufficiently perceptible. The 
casting of a delicate membrane permits the disengagement 
of the limbs and the rapid growth of a golden-yellow pilose 
coat.” The fourth and fifth generations are active wingless 
creatures, which live on the twigs and powder the leaves 
with wool. The sixth generation are winged insects, which 
differ from the early Alatae in their smaller size. They fre¬ 
quent the bark, and there give rise to the seventh generation, 
in which both sexes are present, the male being very 
diminutive. The female lays a single egg, which produces 
the hibernating Fundatrix. 
The remarkable tumours or “ cankers ” not infrequently 
seen on Apple trees are always associated with Myzoxylus 
lanigev (Scliizoncura lanigera ), the so-called “American blight.” 
Descriptions of the insect and its life-history may be found 
in Miss Ormerod’s “ Manual ” and other books on economic 
zoology. The structure and origin of the canker has been 
investigated by Dr. J. E. Blomfield. The deformities are 
produced on the roots as well as the stems and branches. 
The Aphidae do not attack the green terminal part of a twig, 
but select a spot near to the old wood, where the formation 
of a periderm is indicated by the reddish-brown tint. Great 
activity of the cambial region immediately takes place, and 
overgrowth results. The soft parenchymatous tissue splits 
in dry weather, and fungi enter, causing necrosis and 
ulceration, which the plant tries to heal by producing new 
cambial tissue. If this continues long, tumours attaining 
the size of a man’s fist may arise. A striking example of 
the latter condition is shown in Plate XI., which depicts 
part of the branch of an Apple tree bearing thirteen spherical 
tumours, the smallest being about the size of a pea, the 
* “British Aphides," vol. iii. f pp. 98, 99. 
