Violaceae Batsch.

Including Retrosepalaceae Dulac

Habit and leaf form. Herbs, or shrubs, or lianas, or `arborescent' (rarely). The herbs with a basal aggregation of leaves, or with neither basal nor terminal aggregations of leaves. Self supporting, or climbing. Mesophytic, or helophytic. Leaves alternate (usually), or opposite; spiral; petiolate, or petiolate and subsessile, or subsessile; non-sheathing; simple; epulvinate. Lamina entire (usually), or dissected; when dissected, pinnatifid; pinnately veined, or palmately veined; cross-venulate. Leaves stipulate. Stipules free of one another. Leaves without a persistent basal meristem. Domatia recorded (Rinorea); represented by pits (mostly), or hair tufts.

Leaf anatomy. Mucilaginous epidermis often present. Stomata present; anisocytic, or paracytic.

Adaxial hypodermis present, or absent. Lamina dorsiventral (usually), or centric. Minor leaf veins without phloem transfer cells (Viola).

Stem anatomy. Nodes tri-lacunar. Primary vascular tissue in a cylinder, without separate bundles, or comprising a ring of bundles. Secondary thickening developing from a conventional cambial ring. Xylem with libriform fibres, or without libriform fibres; with vessels. Vessel end-walls scalariform, or simple, or scalariform and simple. Wood parenchyma sparse paratracheal (or absent).

Reproductive type, pollination. Hermaphrodite (sometimes cleistogamous). Entomophilous.

Inflorescence, floral, fruit and seed morphology. Flowers solitary (axillary), or aggregated in `inflorescences'; when aggregated, in cymes, or in racemes, or in heads, or in panicles. The terminal inflorescence unit cymose. Inflorescences usually racemes, panicles or heads. Flowers (bi-) bracteolate; fragrant, or odourless; somewhat irregular to very irregular (usually), or regular. The floral asymmetry involving the perianth, or involving the perianth and involving the androecium. Flowers 5 merous; cyclic; tetracyclic. Free hypanthium absent.

Perianth with distinct calyx and corolla; 10; 2 whorled; isomerous. Calyx 5; 1 whorled; polysepalous (usually, more or less), or gamosepalous (at the base); unequal but not bilabiate, or regular; basally appendaged (e.g. Viola), or neither appendaged nor spurred; persistent (often); imbricate, or open in bud; with the odd member posterior. Corolla 5; 1 whorled; polypetalous; imbricate (usually, with descending aestivation), or contorted; unequal but not bilabiate (usually), or regular; spurred (the enlarged anterior member, often), or not spurred. Petals clawed, or sessile.

Androecium 5. Androecial members free of the perianth; free of one another, or coherent; often 1 - adelphous (forming a cylinder round the ovary); 1 - whorled. Androecium exclusively of fertile stamens. Stamens 5; isomerous with the perianth; oppositisepalous. Anthers cohering (often), or connivent, or separate from one another; adnate; introrse; tetrasporangiate; appendaged (the two anterior members often appendaged or spurred, the connective often prolonged), or unappendaged. Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral, or isobilateral, or decussate. Anther wall initially with more than one middle layer (2 to 4). Tapetum glandular. Pollen grains aperturate; 3(-5) - aperturate; colporate; 2-celled.

Gynoecium (2-)3(-5). Carpels reduced in number relative to the perianth (usually), or isomerous with the perianth. Gynoecium syncarpous; eu-syncarpous; superior. Ovary 1 locular. The `odd' carpel anterior. Gynoecium stylate, or non-stylate (Melicytus). Styles 1 (of various forms). Stigmas 1, or 3-5 (Melicytus); truncate (or appendiculate); dry type; papillate; Group III type. Placentation parietal. Ovules in the single cavity 1-100 (to `many'); arillate; anatropous; bitegmic; crassinucellate. Outer integument contributing to the micropyle, or not contributing to the micropyle. Embryo-sac development Polygonum-type. Polar nuclei fusing only after one has been fertilized, or fusing simultaneously with the male gamete (?). Antipodal cells formed; 3; not proliferating; ephemeral (usually), or persistent (Hybanthus concolor). Synergids often hooked (but only rarely with filiform apparatus). Endosperm formation nuclear. Embryogeny asterad.

Fruit fleshy, or non-fleshy; dehiscent, or indehiscent; a capsule, or a berry, or a nut (rarely). Capsules loculicidal and valvular. Fruit when capsular, elastically dehiscent. Seeds endospermic. Endosperm oily. Seeds winged, or wingless. Cotyledons 2 (flat). Embryo chlorophyllous (8 species of Viola); straight.

Seedling. Germination phanerocotylar.

Physiology, biochemistry. Not cyanogenic. Alkaloids present, or absent. Iridoids absent. Proanthocyanidins absent. Flavonols present; kaempferol, or kaempferol and quercetin. Ellagic acid absent (4 genera, 4 species). Saponins/sapogenins present, or absent. Aluminium accumulation demonstrated. Inulin recorded (in Ionidium). C3. C3 recorded in Viola. Anatomy non-C4 type (Viola).

Geography, cytology. Frigid zone to tropical. Cosmopolitan. X = 6-13, 17, 21, 23.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren's Superorder Violiflorae; Violales. Cronquist's Subclass Dilleniidae; Violales. Takhtajan's Subclass Dilleniidae; Dillenianae; Violales. Species 900. Genera 21; Agatea, Allexis, Amphirrhox, Anchietea, Corynostylis, Decorsella, Fusispermum, Gloeospermum, Hybanthus, Hymenanthera, Isodendron, Leonia, Mayanaea, Melicytus, Noisettia, Orthion, Paypayrola, Rinorea, Rinoreocarpus, Schweiggeria, Viola.

Economic uses, etc. Over 120 species of Viola are grown as ornamentals.

Illustrations. viola241.gif viola366.gif

Additional, to be intercalated. Flowers when solitary, axillary.