Oak apple due to the superficial resemblance and the preponderance of the oak marble gall in the wild. Other galls found on oak trees include the oak artichoke gall and the acorn cup gall, but each of these has its own distinctive form. Some common oak-apple-forming species are the "Biorhiza pallida" gall wasp in Europe, "Amphibolips confluenta" in eastern North America, and "Atrusca bella" in western North America. Oak apples may be brownish, yellowish, greenish, pinkish, or reddish. Oak galls have been used in the production of ink since at least the time of the Roman Empire. From the Middle Ages to
Royal Oak three hundred year-old descendant of the original and is thus known as 'Son of Royal Oak'. In 2000, Son of Royal Oak was badly injured during a violent storm and lost many branches. In September 2010, it was found to have developed large and dangerous cracks. Since 2011 the tree has been surrounded by a outer perimeter fence to ensure the safety of visitors. Three third generation descendants of the Royal Oak have been ceremonially planted nearby: Saplings, certified as grown from the Son's acorns, are available from the English Heritage shop at Boscobel House. In commemoration of the tree's