The egg develops into a
larva and then into a full-fledged wasp, boring its way out of the
gall which has served as a protection and nourisher. This accounts for
the hole noticed in almost every gall. The different varieties include
Aleppo. It is found upon the same trees as the valonia and contains 60
to 75 per cent. tannin; Istrian galls, 32 per cent. tannin; Persian,
28 to 29 per cent. tannin. Chinese galls, giving 80 to 82 per cent.
tannin, are the results of the sting of a louse, and make a very
light-colored leather. The dyers also use this material for coloring.
_Knoppern_--Belongs to the family of galls, and is a most important
factor of commerce in Austria. The knopper is generally found on the
acorn or leaf of the oak tree. The greatest quantity is derived from
the steel oak of Hungary. The tannin contained varies from 27 to 33
per cent. Knoppern are not being used so much now as formerly, and
consequently the amount harvested lessens from year to year. Its main
use was and is in combination with valonia as layers for sole leather.
Valonia gives better weight results than knoppern, and is replacing
knoppern more and more every year. The combination of knoppern,
valonia and myrabolams is also quite popular, and gives good results.
Knoppern are seldom used alone, being generally combined with some
other tannin. Austria is almost the only consumer at present, but
Germany used it extensively formerly.
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