SOME FEATURES OF OAK GALL GROWTH. 11 
Positions OccupPrE. 
(a) Root. (b) Stem. (c) Leaf. (d) Flower. 
This section presents the same features as are found 
in all vegetable galls. The division of the plant into 
four primary parts affords the only simple and com- 
prehensive scheme of classification. The student 
desirous of following this phase of the subject is 
referred to the author’s previous work, ‘ British 
Vegetable Galls,’ pp. 24-80. 
Of those on roots there are two galls of distinctive 
and definite forms, Biorhiza aptera and Aphilothrix 
vadicis. While the former has never been found grow- 
ing above ground, the latter is occasionally met with 
on small twigs springing from the tree trunk, at a foot 
or two above the soil (see Plate XXX, div. A). 
The most characteristic gall on the main stem, or 
trunk of the tree, is that of Trigonaspis crustalis, which 
in reality is a transformed bud. Aphilothriv albo- 
punctata is typical of an external gall on the twig, 
and Andricus noduli of a gall concealed within the 
tissues of the twig. Numerous examples could be 
cited of galls attached to the leaf. The mid-rib, its 
off-shoots, the under surface (mostly) of the blade, 
occasionally the upper surface, the margin, and also 
the petiole all have a gall or galls peculiar to them. 
The staminate flowers are attacked, a typical 
example being Aphilothria quadrilineatus. Seven 
other galls are also found on the catkins. The acorn, 
being a subsequent development of a fertilised flower, 
is included in this sub-section, the only gall found 
within the cotyledons being that of Andricus glandium. 
SIMILARITY OF GROWTH. 
There is a remarkable similarity in the appearance 
of many galls of the same or allied genera, especially 
in galls occurring on the continent, but not as yet 
recorded for Britain. The collector of oak galls will 
find upon looking over a collection of European oak 
