General description:- Small shrubs or herbs.
Leaves:- Alternate, stipulate, usually undivided.
Flowers:- Hermaphrodite, solitary. Sepals 5, persistent. Petals 5, free. Stamens 5, introrse, uniting distally (connivent) round the ovary. Ovary superior, single-celled (unilocular), with 3 placentas and numerous ovules.
Fruit:- A 3-valved capsule. Seeds endospermic.
VIOLA
Leaves:- Petiolate. Sepals prolonged into short appendages below the point of their insertion.
The term rosulate is used for plants with a loose, basal rosette of 3-5 petiolate leaves from the axils of which arise flowering branches, and the term arosulate for plants in which this basal rosette is lacking.
Flowers:- Corolla zygomorphic, the lower petal spurred. Connectives of stamens with an apical appendage; the 2 lower stamens spurred. Style thickened above; stigma of various shapes (beaked, bilobed, capitate).
Flower lengths are measured from apex of spur to apex of lower petal, or from apex of upper to apex of lower petal, whichever is the longer.
Fruit:- Seeds with an oily appendage (elaiosome).
Sect. MELANIUM
General description:- Herbaceous.
Leaves:- Stipules usually large, leaf-like, often divided.
Flowers:- Lateral petals directed upwards. Open flowers blue or yellow; self pollinating (cleistogamous) flowers not produced. Style bent, knee-like (geniculate) at the base, pin-headed (capitate), with wide stigmatic aperture.
Sect. VIOLA
General description:- Herbaceous.
Leaves:- Stipules not leafy.
Flowers:- Open flowers blue, violet or white; self fertilizing (cleistogamous) flowers produced. Style beaked at apex.
Subsect. VIOLA
General description:- Perennial; acaulescent, sometimes stoloniferous.
Fruit:- Capsules globose, not explosive, on decumbent peduncles. Seeds with conspicuous elaiosome.