AN ENCYCLOPADIA 
OF HORTICULTURE. 
Oak Galls—continued. 
either by lower plants (Fungi), or by animals, which pro- 
duce the Galls either for the protection of their young 
T and immature larvæ, or for their own protection at all 
stages of development. The makers of Oak Galls belo 
almost entirely to the great group of Hymenoptera, know: 
725 as Cynipide, or True Gall Flies, almost the only excep- 
he 3 being a few Midges, which merely fold down the 
`s, lobes of leaves, making them become fleshy. 
Taue Cynipide are all of small size, seldom exceeding 
i $2, zin. in length, with a rather greater spread of wing. 
8 They vary a good deal in colour—from reddish-brown 
do black—and frequently show metallic reflections. The 
nmuings are supported by a few nerves. The females pos- 
sess, at the tn of the abdomen, an ovipositor, and, by 
means of this organ, which is frequently of considerable 
, they bore into some parts of the tree, and thereby 
rise to the Gall.” 
Galls are found growing from every part of Oak-trees, 
from roots and branches, to leaves, stamens, and ovaries, 
or fruits; and, in harmony with such diversity of situa- 
tion, they vary exceedingly in their appearance, consist- 
2a 3 internal structure; but all those of the Cyni- 
. E Fic. 705. Oak GALLS. 
ae * 
4, Gall of, Dryoteras terminalis (Oak Apple), about two-thirds 
natural size. 
oe bearing Galls of Biorhiza aptera, about 
* Tome Boa d O size. hea Galls vary much in size, and are 
often crowded into a mass, and fused together. When fresh, 
they are red, and rather fleshy ; but, in yig iey become 
dark brown and They are believed to the autumn 
2 form of the cycle to which “Oak Apples” belong as the 
a summer form. The insects that emerge from them are all 
wingless females. 
The f Biorhiza aptera (see Fig. 705) is one of the 
8 The others do not call for further notice 
here. Galls on the main stems are not very numerous. 
Far more se ting: » 
the branches. y 
sail e others are conspicuous Galls formed upon the 
leaves, usually on their lower surface; and still others 
are stamens or ovaries, changed in structure by the 
minute thin-walled chambers, each occupied by one 
and important are those formed 
of these are modified buds; | 
Oak Galls—continued. „ 
punctures of the parent insects. On the Continent of 
Europe, nearly 100 different fo je 
found on Oaks; and in Britain 
already observed reaches nearly forty. 3 
more widely-known Galls may be mentioned the Oak 
Apple (see Fig. 705), found, in May and June, on 
the twigs, as an oblong mass, from * 
long, covered with a smooth, green and red skin, above 
a layer of soft tissue, in which are imbedded numerous 
larve, each one in a hard -walled cell or chamber in 
the centre of the Gall. The Cotton Gall resembles a 
ball of white cotton wadding surrounding a number of 
larva of small size. The whole mass may reach a size 
of lin. or more across, and is very conspicuous, as it 
hangs attached to the male catkins in May and June. 
The Devonshire, or Marble, Gall of the Oak is very 
easy to recognise, as it is about the size and form of a 
boy’s marble, green and soft when young, but brown 
and hard when mature. Two or more of the Galls often 
join together during growth, and form irregular masses. 
In the centre is a small cavity, inhabited by the larva. 
It is said that this Gall was introduced from the Con- 
tinent, and was first observed in Devonshire; but, what- 
ever ita origin, it is now abundant in many parts of 
Britain, Experiments have not succeeded in rearing 
males, but have yielded many female Gall insects from 
these Galls, and, along with them, seventy or more kinds 
of insects that live in the Galls, either as guests 
(inquilines) or as true parasites. The name of the Gall- 
maker is Oynips Kollari. The Artichoke Gall, formed 
by Aphilothria gemme, very much resembles a miniature 
Artichoke, about lin. long, formed of scales, with a central 
chamber like a small acorn. Various kinds of bud Galls `“ 
are too small to be fonnd without careful search, and 
are of interest chiefly because of the relation of some 
of them to other conspicuous forms that disfigure young 
Oak-trees in pleasure grounds. 
The leaves bear many curious forms of Galls, some 
of them so conspicuous that they cannot have escaped 
the notice of even the least observant. One that causes 
B 
* Fic. 706. OAK GALLS. Š 
=. f Galls of Andricus curvator in Oak Leaves, about 
y Lo 5 Gall in Transverse Section, showing small 
inner Gall. i 
B, Oak Twig, with two Galls of Aphilothria collaris, natural size. 
damage is the work of Andricus curvator (see 
2 706). It is produced on the midrib, or leafstalk, 4 
and causes a marked bend, or twist, in the leaf, or a 
at its base in the branch; the Gall forms a green ak 
swelling, about the size of a pea. Inside this lies a 
small, brown, kidney-shaped inner Gall, which, when 
ripe, is quite free from the inside of the wall of the 
large chamber. The Currant Galls, resembling trans- 
Tucent currants, pale, with purple or red mottlings, 
