The dried excrescences from certain trees and
shrubs, especially Oak galls (Quercus infectoria),
from the Near East and Eastern Europe; Chinese
galls (Rhus semialata), from the Far East;
Tamarisk galls, from several species of Tamarix,
located from Morocco to India; and Pistacia galls,
from several European and Indian species of
Pistacia. All are relatively rich in tannin (36 to
60%) and are said to contain free gallic acid in
addition to tannin, as well as an easily soluble
form of ellagic acid. In general, the tannin is
not homogeneous and is believed to be built up as
a polygallol-ellagic acid.
The galls result from the plants reaction to
irritation caused by the larvae of various insects
which lay eggs in the cambium area of the plants.
Although galls were used extensively over a period
of centuries in the manufacture of certain inks,
and in the tanning of leather, they are little
used today for tanning outside of the areas where
they are collected, largely because of the expense
involved in their collection. See also: IRON-GALL INK ; VEGETABLE TANNINS .
(175 , 235 , 363 )