The Linaceae is a family of flowering plants. The family is cosmopolitan, and includes approximately 250 species. There are 14 genera, classified into two subfamilies: Linoideae and Hugonioideae (often recognized as a distinct family, the Hugoniaceae). Leaves of Linaceae are always simple; arrangement varies from alternate (most species) to opposite (in Sclerolinon and some Linum) or whorled (in some Hesperolinon and Linum). The hermaphroditic, actinimorphic flowers are pentameric, or very rarely tetrameric (e.g. Radiola linoides, Linum keniense).
In Linoideae, the largest genus is Linum, the flaxes, with 180-200 species including the cultivated flax, Linum usitatissimum. Members of Linoideae include herbaceous annuals and perennials as well as woody subshrubs, shrubs, and small trees (Tirpitzia) inhabiting temperate and tropical latitudes of Eurasia, Africa, Australia, and the Americas. The largest genus of Hugonioideae is Hugonia (~40 spp); Hugonioideae are woody vines, shrubs, and trees and are almost entirely tropical in distribution. In addition to their growth habits and geographic distributions, Linoideae and Hugonioideae can be differentiated by the number of fertile stamens (5 in Linoideae, 10 in Hugonioideae) and fruit type (capsules in Linoideae, fleshy drupe-like fruits in Hugonioideae).
Genera in subfamily Linoideae
- Anisadenia
- Cliococca
- Hesperolinon
- Linum
- Radiola
- Reinwardtia
- Sclerolinon
- Tirpitzia
Genera in subfamily Hugonioideae
- Durandea
- Hebepetalum
- Hugonia
- Indorouchera
- Philbornea
- Roucheria
Under the old Cronquist system of classifying the flowering plants, the Linaceae was placed in its own order Linales. Modern classifications place it in the order Malpighiales.