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, Michigan featuring restaurants, shopping, and entertainment. A number of mixed-use high-rise developments have been constructed — mostly condo "lofts" with retail and office space on the lower levels. Points of interest include the Detroit Zoo, a major regional tourist attraction, the William Beaumont Hospital, the Royal Oak Music Theatre, the Main Art Theatre, the Baldwin Theatre, Mark Ridley's Comedy Castle, Emagine Theater, and shops, cafes, and restaurants. The main offices of Hour Detroit media, which publishes Metro Detroit's lifestyle magazine, are located in the city. The National Arbor Day Foundation has awarded Royal Oak the distinction of "Tree City USA" every