Oak apple

The rotund gall is a plant gall, which occurs on the underside of oak leaves in autumn. It arises from laid fertilized eggs of the Eichengallwespe ( Cynips quercusfolii ).

Inside the Gallapfels (also Folii - bile or bile sheet called ) is a larva then hatches always the female insect in the autumn, which ever puts an unfertilized egg in the growing tip of the oak bud. This wintered there and forms from the spring buds Gallen ( Taschenbergii - Gallen), from which then slip both males and females of the Eichengallwespe in June. The fertilized females lay eggs again with the help of the ovipositor in a leaf vein Oak leaf from. Through a defensive reaction of the oak is formed around the layering position the morbid growth, which is called due to the spherical shape of gall.

Commercial use

The gall contains, among other 55-65 % tannic acid ( tannin) and gallic acid. The decoction of coarsely ground galls supplies with iron and copper salts (eg, iron sulfate), dark and deep connections that is as black ink, called iron gall ink, still used today in the signing of treaties, but was also used as a tanning agent for leather tanning. On the former site of a specialized in the processing of galls mill has the name of the Kaiserslautern district towards Galappmühle.

In addition to the gall there are growths on oak trees, which are also caused by the oviposition of the gall wasp, which are not spherical, contain only 25-28% tannins, Knopper (plural: Knoppern ) are mentioned and also used commercially and were traded as a commodity.

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