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Sorbus (family Rosaceae) A genus of trees and shrubs with simple or pinnate leaves, and no thorns. They are similar to Pyrus (pear) in flower structure, with 5 petals, and many stamens, but the cartilaginous carpel walls are not completely united to the apex in the fruit, and the flowers are borne in compound corymbs, not simple, umbel-like inflorescences. The genus includes S. aucuparia (rowan or mountain ash), S. aria (whitebeam), and S. torminalis (wild service tree). There are about 85 species, some taxonomically very critical, occurring in northern temperate regions.