VIOLACEAE

Violaceae is a family of flowering plants established in 1802, consisting of about 1000 species in about 25 genera. It takes its name from the genus Viola, the violets and pansies.

Older classifications such as the Cronquist system placed the Violaceae in an order named after it, the Violales or the Parietales. However, molecular phylogeny studies place the family in the Malpighiales as reflected in the Angiosperm Phylogeny Group (APG) classification, with 41 other families, where it is situated in the parietal clade of 11 families. Most of the species are found in three large genera, Viola, Rinorea and Hybanthus. The other genera are largely monotypic or oligotypic. The genera are grouped into four clades within the family. The species are largely tropical or subtropical but Viola has a number of species in temperate regions. Many genera have a very restricted distribution.

Though the best-known genus, Viola, is herbaceous, most species are shrubs, lianas or small trees. The simple leaves are alternate or opposite, often with leafy stipules or the stipules are reduced in size. Some species have palmate or deeply dissected leaves. Many species are acaulescent. The flower are solitary in panicles. Some species have cleistogamous flowers produced after or before the production of typical flowers with petals. Flowers are bisexual or unisexual (e.g. Melicytus), actinomorphic but typically zygomorphic with a calyx of five sepals that are persistent after flowering. Corollae have five mostly unequal petals, and the anterior petal is larger and often spurred. Plants have five stamens with the abaxial stamen often spurred at the base. The gynoecium is a compound pistil of three united carpels with one locule. Styles are simple, with the ovary superior and containing many ovules. The fruits are capsules split by way of three seams. Seeds have endosperm.

The Violaceae have an overall cosmopolitan distribution, but are essentially tropical and subtropical, with the exception of the numerous Northern Hemisphere temperate species of Viola, the largest genus, which also occurs at higher altitudes in its tropical and subtropical regions, where the shrub, tree and lianescent species are concentrated. In those regions, most representative genera are the mainly woody Rinorea and Hybanthus. While Viola, Hybanthus, and Rinorea are widely distributed in both hemispheres, the remaining genera are relatively restricted in their distribution. Some are restricted to a single continent while others have a limited area involving just a single archipelago. About 70 species are found in Brazil.


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