The rounded gall apple , also called oak gall , oak gall and leaf gall (from Latin galla ), is a plant gall that occurs in autumn on the underside of oak leaves , especially of Quercus infectoria , but also of the sessile oak and the pedunculate oak . It arises from deposited fertilized eggs of gall wasps (Cynipidae), such as the common oak gall wasp ( Cynips quercusfolii ).
Inside the gall apple there is a larva , from which the always female insect hatches in autumn, which each lays an unfertilized egg in the vegetation cone of the oak bud. This hibernates there and forms bud galls ( Taschenbergii galls ) from spring , from which both males and females of the oak gall wasp hatch in June. The fertilized females then lay eggs again in a leaf vein of the oak leaf with the help of the laying spike. A defensive reaction of the oak creates the pathological overgrowth around the laying area, which is called the gall apple due to its spherical shape.
The gall apple contains up to 60% tannic acid ( tannin ) and gallic acid and therefore tastes astringent sour. The decoction of coarsely ground galls supplies with iron salts (e.g. iron (II) sulfate ) deep dark compounds, which as a black ink , called iron gall ink , but also as a tanning agent for the tanning of leather was used. The name of the Kaiserslautern district Galappmühle refers to the former location of a mill specializing in the processing of gall apples .
In addition to the gall apple, there are also growths on oaks, which are also triggered by the oviposition of the gall wasps , which are not spherical and contain only 25–28% tannins. They are called knoppers (plural: knoppers), were also used commercially and traded as raw materials.
- Thomas Gleinser: Anna von Diesbach's Bernese 'Pharmacopoeia' in the Erlacher version of Daniel von Werdts (1658). Part 2: Glossary (= Würzburg medical historical research. Volume 46). Wellm, Pattensen / Han., Now published by Königshausen & Neumann, Würzburg 1989 (at the same time: Medical Dissertation Würzburg 1989), ISBN 3-921456-86-X , p. 111.
- Ernst Küster: Contributions to the knowledge of the biliary anatomy. In: Flora or general botanical newspaper. Volume 87, 1900, pp. 117-193.
- See for example Jürgen Martin: The 'Ulmer Wundarznei'. Introduction - Text - Glossary on a monument to German specialist prose from the 15th century. Königshausen & Neumann, Würzburg 1991 (= Würzburg medical-historical research. Volume 52), ISBN 3-88479-801-4 (also medical dissertation Würzburg 1990), p. 129 ( Galla ).
- Old recipe for iron gall ink. In: Planet Knowledge. March 13, 2015, accessed November 7, 2018 .