Oak apple
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An oak apple or oak gall is a large, round, vaguely apple-like gall commonly found on many species of oak. Oak apples range in size from 2 to 4 centimetres in diameter and are caused by chemicals inje
Oak apples on Quercus robur leaf
Oak galls on a Pyrenean oak (Quercus pyrenaica) in León, Spain.
An oak apple on a tree in Worcestershire, England
An oak apple on an oak leaf.
Gall
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Galls or cecidia are a kind of swelling growth on the external tissues of plants. Plant galls are abnormal outgrowths of plant tissues, similar to benign tumors or warts in animals. They can be caused
Oak apple
…An oak apple or oak gall is a large, round, vaguely apple-like gall commonly found on many species of oak. Oak apples range in size from 2 to 4 centimetres (1 to 2 in) in diameter and are caused by chemicals injected…
Cola-nut galls (Andricus lignicola) on pedunculate oak, caused by a cynipid gall wasp
Oak artichoke gall caused by Andricus foecundatrix
Artichoke gall cut open to reveal wasp larva
Knopper gall caused by Andricus quercuscalicis