Linaceae is a family of flowering plants. The family is cosmopolitan, and includes about 250 species in 14 genera, classified into two subfamilies: the Linoideae and Hugonioideae (often recognized as a distinct family, the Hugoniaceae). Leaves of the Linaceae are always simple; arrangement varies from alternate (most species) to opposite (in Sclerolinon and some Linum) or whorled (in some Hesperolinon and Linum species). The hermaphroditic, actinomorphic flowers are pentameric or, very rarely, tetrameric (e.g., Radiola linoides, Linum keniense). In the Linoideae, the largest genus is Linum, the flaxes, with 180–200 species including the cultivated flax, Linum usitatissimum.