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Published In: Species Plantarum 2: 933. 1753. (1 May 1753) (Sp. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library

Project Name Data (Last Modified On 9/22/2017)
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2. Viola L. (violet)

Plants annual or perennial herbs, with taproots or rhizomes, respectively. Aerial stems absent or, if present, then mostly less than 35 cm tall at flowering, erect, ascending, or spreading with ascending tips, unbranched or more or less dichotomously few-branched, with up to 6 nodes, glabrous or hairy. Leaves all basal or (in species with aerial stems) also alternate, the basal leaves long-petiolate, the stem leaves short- to more commonly long-petiolate. Stipules various, often relatively conspicuous, entire, toothed, or dissected into several, deep, jagged lobes. Inflorescences of solitary flowers, these axillary in species with aerial stems, appearing basal in taxa not producing aerial stems, the flowers mostly long-stalked, with a pair of small, herbaceous bracts positioned variously on the jointless stalk. Calyces of 5 free sepals, each of these with a sometimes inconspicuous saclike auricle at the base. Corollas of 5 free petals, 4–30 mm long, white or pale cream-colored to yellow, orange, bluish purple, or multicolored, the throat yellow or greenish white, the lowermost petal short- to long-spurred. Stamens 5, the filaments adjacent but free, the lowermost pair bearing nectaries inserted into the petal spur, the anther appendages relatively large, oblong-ovate, entire, membranous, orange. Style linear or strongly thickened toward the tip (club-shaped), often appearing slightly curved above the midpoint, the stigma variously shaped, often lobed or positioned obliquely. Fruits 4–15 mm long, oblong-ovoid to oblong-ellipsoid, usually green at maturity, sometimes darker in cleistogamous flowers, in some species dehiscing explosively. Seeds 9 to many per carpel, narrowly ovoid to obovoid or globose, the surface usually appearing dull, finely pebbled or minutely roughened, variously colored, usually with an aril. About 525 species, nearly worldwide.

Viola is the largest genus in the family and has been classified historically as comprising several sections and subsections, some of which have a well-deserved reputation as taxonomically difficult (especially in the so-called stemless groups that do not produce aerial stems). Much of the controversy involves differing opinions as to whether perceived morphological differences are representative of relatively cryptic species or whether these differences are the result of minor differentiation between populations that is maintained through the production of cleistogamous flowers. Cleistogamous flowers are produced later in the growing season by many species and are obligately self-pollinated. Their stalks often are a different length or positioned differently, and at maturity such flowers resemble young buds (the corollas are poorly developed and the calyces remain closed over the stamens and ovary at maturity).

For many years, most botanists followed the taxonomic summary of North American violets by Russell (1965), although this relatively preliminary treatment contained insufficient comparative taxonomic data to address difficulties encountered in determining specimens of Viola. More recently, three researchers have focused on the taxonomy of the stemless blue violets of eastern temperate North America, with the result that botanists have a choice between three somewhat discordant treatments published over a five-year period (McKinney, 1992; Ballard, 1994; Gil-Ad, 1997; and other papers by these authors). Ultimately, resolution of taxonomic controversies in some groups must await further, more intensive studies involving a broad sampling of populations and analysis of molecular markers. Further notes are included below in the discussions of selected taxa. The present treatment is adapted and updated from the author’s earlier study of the Michigan violets (Ballard, 1994).

The attractive flowers of the stemless blue-flowered species are used in a delicious and beautiful jelly, candied for unique confections, and eaten in salads. The leaves also harbor significant amounts of vitamin C and are edible as a nutritious potherb in spring. Steyermark (1963) noted that the young foliage of most of the stemless blue violets is mucilaginous and can be eaten raw or cooked, with a texture similar to that of okra.

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