Violaceae

Abstract

Trees, treelets, shrubs or subshrubs, infrequently lianas or herbs, sometimes stoloniferous. Leaves alternate, sometimes opposite, distichous or pseudo-whorled, pinnately or rarely palmately veined, entire or rarely lobed or dissected, with conspicuous persistent or sometimes deciduous stipules, petiolate or sometimes subsessile, epulvinate; plants glabrous or variously pubescent with unicellular or multicellular hairs. Inflorescences thyrso-paniculate, botryoids (pseudo-racemes, compound or simple cymes), fascicles or condensed "short shoots”, or flowers solitary; inflorescences subtended by a commonly persistent bract; pedicels commonly articulated, almost always bearing a pair of prophylls; flower buds in Viola and some other strongly zygomorphic genera becoming resupinate at anthesis, with saccate or spurred petal lowermost. Flowers bisexual (unisexual), actinomorphic to strongly zygomorphic, hypogynous (slightly perigynous); sepals 5, free, typically quincuncially arranged, persistent through fruiting, equal in actinomorphic flowers, slightly unequal or rarely strongly unequal in zygomorphic ones; petals 5, free, rarely persistent into fruit, equal in actinomorphic flowers, the anterior slightly to much longer and saccate or spurred in zygomorphic flowers, aestivation commonly apotact sensu Hekking (1988b), sometimes quincuncial or rarely convolute; stamens 5(3), free or filaments weakly to strongly connate into a tube; anthers dithecal, introrse, rarely extrorse, commonly bearing a dorsal sterile connective appendage, occasionally with two ventral connective appendages; in zygomorphic flowers 2 filaments and/or dorsal surfaces of the anthers bearing individual or fused nectariferous glands enclosed by a sac or spur at the base of a differentiated petal; ovary superior, (2)3(4-5)-carpellate, unilocular with parietal placentas; ovules 1-many, anatropous, bitegmic, crassinucellate; style filiform or sometimes clavate, straight, curved or sigmoid; stigma often simple, less often rostrate, orifice porrect or bent downward especially in zygomorphic flowers. Fruits commonly a capsule dehiscing with (2)3(4-6) coriaceous to woody, rarely elastic or papery valves, sometimes fleshy, rarely a nut. Seeds in most genera uniform, globose to narrowly ellipsoid, compressed to strongly flattened and often with an intermittent to entire wing in a few genera, rarely of two types (spindle-shaped and discoid), in some genera bearing elaiosomes; endosperm nuclear, oily; embryo flat, straight.