The family Gesneriaceae - basic information

Full name: Gesneriaceae [Rich. &  Juss. ex] DC. 

Formal publication: A. P. de Candolle, Essai propr. méd. pl., ed. 2: 192 (1816) ("Gessnerieae").

Synonyms: Belloniaceae Martinov (1820), Didymocarpaceae D.Don (1822), Cyrtandraceae Jack (1823), Besleriaceae Raf. (1838), Ramondaceae Godr. (1850).

Description: Perennial (very rarely annual) herbs, subshrubs, shrubs or small trees; perennial herbs with fibrous roots or with rooting above- or underground stems, rootstocks, rhizomes, scaly rhizomes, or tubers; terrestrial, epiphytic or climbing. Stem erect, ascending, decumbent, creeping, pendulous, or ± absent. Leaves opposite, sometimes in whorls of three or four, or in near-distichous or spiral-alternate arrangement; usually petiolate; stipules absent; lamina usually undivided, very rarely lobed or pinnately dissected. Number of leaf pairs sometimes reduced to the cotyledonary pair, with one of the two cotyledons growing up to a large, foliar organ. Indumentum of stem and leaves of glandular and eglandular hairs, rarely absent. Inflorescences a foliose or (rarely) bracteose indeterminate thyrse with axillary, pair-flowered cymes; cymes sometimes reduced to solitary flowers. Flowers usually showy, zoophilous, rarely auto- or cleistogamous, 5- (very rarely 4-)merous. Sepals free or connate to a variable extent, equal or unequal and then calyx two-lipped. Corolla sympetalous, zygomorphic with bilabiate limb, rarely actinomorphic; shape variable, long-tubular, infundibuliform, funnel-shaped, campanulate to flat-rotate; white, blue, violet, red, orange, yellow, greenish, brownish, or various colours combined, with or without markings. Stamens mostly 4 or 2, rarely (in the actinomorphic flowers) 5; 1 or 3 staminodes usually present. Filaments always adnate to the corolla, inserted at the base, the middle or near the mouth of the corolla, either long and slender, in the tetrandrous species often didynamous, or very short; anthers of variable shape, basi- or (rarely) dorsifixed, dithecal, opening by longitudinal slits or by apical or basal pores; very often cohering at apex or face to face, in the tetrandrous-didynamous species the anthers cohering in pairs or all 4. Nectary either adnate to ovary base or free; annular or divided into separate glands, or absent. Ovary syncarpous, composed of two median (upper and lower) carpels; mostly unilocular with lateral, T-shaped placentae; rarely bilocular with axile placentae, rarely one carpel sterile; ovary superior, semi-inferior or inferior; style usually well developed; stigma capitate, bilabiate or variously bifid; ovules numerous, anatropous, unitegmic, tenuinucellate. Fruit dehiscent (a dry or fleshy capsule) or indehiscent (a sclerocarpous or fleshy berry); capsules elongate, ovoid or globose, opening septicidally or loculicidally by 2 or septicidally plus loculicidally by 4 valves or along the midrib of the upper carpel only ("follicular" type, in this case the capsule is held horizontally); fleshy berries sometimes vividly coloured. Seeds numerous, small, usually oval or polygonal in outline; dispersed by wind, water (rain), birds, or ants. Testa frequently reticulate, often with various additional ornamentations. Endosperm single- or several-layered. Embryo with two equal cotyledons. One cotyledon growing faster than the other in the paleotropical Gesneriaceae (anisocotyly).

Number of genera: between 150 and 160, depending on the taxonomic concepts of particular genera.

Number of species: more than 3200.

Size of genera: the largest genus is Cyrtandra with perhaps 600 species, followed by Columnea s.l. (over 270 spp.) and Besleria (over 200 spp.). Some 40 genera comprise only a single species.

Distribution: mainly in the tropics and subtropics of the Old and the New World, with transgressions to the north (Europe: Pyrenees, Balkan Peninsula; Asia: Himalayas, China incl. N China) and the south (SE Australia, New Zealand, S Chile). Both in Asia-Malesia and in America there are around 60 genera; in Africa there are 9 genera (c. 160 spp.), in Europe 3 genera (6 species). Nine genera (20 spp.) have a distinctly southern hemisphere distribution. Only one genus, Rhynchoglossum, is represented both in Asia and (with a single species) in the neotropics. The second genus with transcontinental distribution is Epithema (one species in W Africa, the other (ca. 20) species in Mainland Asia and Malesia).