268 
QUERCUS INFECTORIA. 
of the Archipelago as far as the frontiers of Persia. It has a 
crooked stem, seldom exceeds six feet in height, and more frequently 
assumes the character of a shrub than that of a tree; the leaves, 
which are deciduous in autumn, are on short petioles, smooth, of a 
bright green colour on both sides, and obtusely toothed; the acorn 
is elongated, smooth, two or three times longer than the cup, which 
is sessile, in a slight degree downy, and scaly ; the gall comes at the 
shoots of the young boughs, and acquires from four to twelve Hues 
in diameter : the insect which produces it, is the Cynips Quercusfolii 
of Linnaeus (Diplolepsis Gallae Tinctoriae of Geoffroy) a small hyme- 
nopterous insect, or fly, with a fawn coloured body, dark antenna;, 
and the upper part of the abdomen of a shining brown. The insect 
punctures the tender shoot with its sting, which is spiral, and depo- 
sits its eggs in ihe puncture : this occasions a morbid irritation in 
the vessels of the part, the gall rises in a few hours, and attains its 
full size in a day or two, before the larva is hatched. The egg grows 
with the gall, and it is the irritation wliich it keeps up, not, as has 
been supposed, by the maggot feeding on the juices of the plant, 
that the morbid excitement is maintained in the vessels of the part, 
sufficient for the production of this kind of vegetable wen. 
Sensible and Chemical Qualities of Galls. Galls are 
nearly spherical, and vary in magnitude from the size of a pea to 
that of a large hazel nut; they are smooth or knotty on the surface, 
of a greenish drab colour, some have a reddish or blue tint, and 
are generally perforated with a small hole ; they are heavy, brittle, 
and break with a flinty fracture. Internally they consist of a spongy, 
striated, but hard substance, of a yellowish colour. They have little 
or no odour, but a bitter and powerfully astringent taste. The best 
galls are those of a bluish or blackish colour, heavy and tuberculated 
on the surface. Those that are light and spongy, and of a pale colour, 
are of an inferior quality. The soluble part of galls is taken up by 
about forty times its weight of boiling water, the residue is tasteless. 
Alcohol takes up nearly seven parts out of ten, and ether five. 
Neumann obtained from 9G0 grains of coarsely powdered galls, 840 
watery extract, and afterwards 4 alcoholic ; and inversely, 760 alco- 
holic, and 80 watery. From the analysis of Sir H. Davy, we learn 
that 500 grains of Aleppo galls yielded to pure water by lixiviation, 
185 grains of solid matter, of which 130 were tannin ; mucilage and 
matter rendered insoluble by evaporation, 12 ; gallic acid, and a 
little extractive matter, 31 ; saline and earthy matter, 12. A satu- 
rated decoction of galls, on cooling, deposits a copious pale yellow 
precipitate, which appears to be purer tannin than can be got by any 
