The World Flora Online

SELECTED REFERENCES

Al-Shehbaz, I. A. and B. G. Schubert. 1989. The Dioscoreaceae in the southeastern United States. J. Arnold Arbor. 70: 57–95. Ayensu, E. S. 1972. Dioscoreales. In: C. R. Metcalfe, ed. 1960+. Anatomy of the Monocotyledons. 8+ vols. Oxford. Vol. 6. Bouman, F. 1995. Seed structure and systematics in Dioscoreales. In: P. J. Rudall et al., eds. 1995. Monocotyledons: Systematics and Evolution. 2 vols. Kew. Vol. 1, pp. 139–156. Burkill, I. H. 1960. The organography and evolution of the Dioscoreaceae, the family of yams. J. Linn. Soc., Bot. 56: 319–407. Caddick, L. R. et al. 1998. Microsporogenesis and pollen morphology in Dioscoreales and allied taxa. Grana 37: 321–336. Caddick, L. R. et al. 2000. Yams and their allies: Systematics of Dioscoreales. In: K. L. Wilson and D. A. Morrison, eds. 2000. Monocots: Systematics and Evolution. Melbourne. Pp. 475–487. Coursey, D. G. 1967. Yams: An Account of the Nature, Origins, Cultivation and Utilisation of the Useful Members of the Dioscoreaceae. London. Huber, H. 1998. Dioscoreaceae. In: K. Kubitzky et al., eds. 1990+. The Families and Genera of Vascular Plants. 4+ vols. Berlin etc. Vol. 3, pp. 216–235. Knuth, R. 1924. Dioscoreaceae. In: H. G. A. Engler, ed. 1900–1953. Das Pflanzenreich…. 107 vols. Berlin. Vol. 87 [IV,43], pp. 1–387. Queva, C. 1894. Recherches sur l’Anatomie de l’Appareil Vegetatif des Taccacées & Dioscorées. Lille.

Vines [herbs], geophytes perennating from fleshy rhizomes or tubers. Stems renewed annually or occasionally persisting for more than a single growing season, twining-climbing, procumbent, or seldom erect; vascular bundles commonly arranged in 2 concentric circles. Leaves alternate, opposite, or whorled at basal nodes; blades simple or occasionally digitately compound, typically cordate, reticulate-veined; principal veins arcuate, ascending from base to apex; margins entire or sometimes palmately lobed; stipules absent, rarely stipulate, never with tendrils; petioles typically with distinct pulvinus at each end. Inflorescences axillary, solitary or in fascicles of 2–7, branched and paniculate, or unbranched and spicate or racemose, ultimate inflorescence unit cymose, sessile or pedunculate, often reduced to 1 flower. Flowers unisexual, staminate and pistillate flowers on different plants, rarely staminate and pistillate flowers on same plant or bisexual; perianth epigynous, rotate, campanulate, or funnelform; tepals 6, petaloid, in 2 similar whorls of 3, connate at least basally; stamens 6, in 2 whorls of 3, inner whorl sometimes sterile or absent; filaments distinct [connate basally or completely into tube], inserted at base of perianth; anthers 2-locular, tetrasporangiate, dehiscing by longitudinal slits, thecae distinct or sometimes connate, rarely divided by a long-appendiculate connective; pistils 3; ovary (1–)3-locular, ovules anatropous, 2(–many) per locule, placentation axile or parietal; styles 3, ± distinct. Fruits capsular, rarely baccate or samarate, dehiscence loculicidal. Seeds flattened or globose, winged or unwinged, embryo small, endosperm copious, starchless.

Herbes rhizomateuses, vivaces, généralement dioïques ; rhizome souvent réduit à une petite couronne au sommet d’un à plusieurs tubercules annuels ou pérennes, riches en amidon ; tiges herbacées, volubiles, dépourvues de vrilles. Feuilles opposées à alternes, simples à composées ; pétiole avec renflement (pulvinus) basal et apical ; limbe à base souvent cordée, à nervures toutes basilaires, s’étalant puis convergeant vers le sommet. Inflorescences axillaires, à fleurs solitaires, en panicules, cymes, épis ou racèmes. Fleurs 3-mères, presque toujours actinomorphes, unisexuées ou parfois bisexuées ; tépales 6 ; étamines généralement 6 ; ovaire infère, 3-loculaire, avec 2 à plusieurs ovules par loge. Fruits des capsules, à déhiscence loculicide irrégulière. Graines aplaties et ailées, ou sans ailes et soit globuleuses et lisses, soit irrégulières et ruminées.

Une famille avec aujourd’hui 637 espèces réparties en trois genres, dont 633 dans le genre Dioscorea. La famille est présente en régions (sub)tropicales et tempérées chaudes du monde entier. La diversité générique est la plus élevée en Asie du Sud-Est ; la diversité des espèces est la plus élevée dans les régions tropicales saisonnièrement sèches, en particulier en Amérique du Sud centrale, au Mexique, dans les Caraïbes, en Afrique du Sud, à Madagascar et en Asie du Sud-Est. Au Gabon, seule le genre Dioscorea est présent.

Style 3, free or connate Staminodes 0, 3 or 6 Ovary inferior, 3-locular Rudimentary ovary frequent Female inflorescences: spikes looser, longer than the male ones, solitary or paired or sometimes more numerous, in the leaf axils Stamens 6, or 3 with or without 3 staminodes Filaments free or shortly connate; anthers 2-locular Bracteole generally present in oblique position Flowers placed singly along the axis or in short few-flowered lateral cymules Flowers small, inconspicuous, actinomorphic Male flowers sessile or shortly pedicelled Inflorescence spicate, racemose or paniculate Plants dioecious; exceptionally on the same inflorescence are clustered male and female flowers6 Leaves moving, following the conditions of lighting Basal leaves often reduced Petiole generally twisted and sometimes jointed at the base or with more or less leathery auricles Leaves alternate or opposite (sometimes both on the same plant), often cordate, entire or lobulate, more or less digitately nerved or palmately compound, acumen often large and glandulose Stems glabrous or pilose Male inflorescences: spikes generally several in the leaf axils, sometimes clustered in racemes or compound panicles Perianth campanulate or spreading, 6-lobed, lobes 2-seriate, often connate at the base Seeds winged, with albumen Fruits (in the tropical African species) 3-valved capsules Placentation axile: 2 anatropous ovules in each loculus Climbers (at least the West African species), spiny or not, annual or perennial with tubers annually renewed or perennial Tubers toxic or edible, often protected by thorny roots Aerial tubers (bulbils) present or absent Staminodes 0, 3 or 6 Ovary inferior, 3-locular Rudimentary ovary frequent Female inflorescences: spikes looser, longer than the male ones, solitary or paired or sometimes more numerous, in the leaf axils Stamens 6, or 3 with or without 3 staminodes Filaments free or shortly connate; anthers 2-locular Bracteole generally present in oblique position Flowers placed singly along the axis or in short few-flowered lateral cymules Flowers small, inconspicuous, actinomorphic Male flowers sessile or shortly pedicelled Inflorescence spicate, racemose or paniculate Plants dioecious; exceptionally on the same inflorescence are clustered male and female flowers6 Leaves moving, following the conditions of lighting Basal leaves often reduced Petiole generally twisted and sometimes jointed at the base or with more or less leathery auricles Leaves alternate or opposite (sometimes both on the same plant), often cordate, entire or lobulate, more or less digitately nerved or palmately compound, acumen often large and glandulose Stems glabrous or pilose Male inflorescences: spikes generally several in the leaf axils, sometimes clustered in racemes or compound panicles Perianth campanulate or spreading, 6-lobed, lobes 2-seriate, often connate at the base Seeds winged, with albumen Fruits (in the tropical African species) 3-valved capsules Placentation axile: 2 anatropous ovules in each loculus Climbers (at least the West African species), spiny or not, annual or perennial with tubers annually renewed or perennial Tubers toxic or edible, often protected by thorny roots Aerial tubers (bulbils) present or absent

Fls trimerous, regular, epigynous, unisexual (the plants dioecious) or seldom perfect; tep in 2 similar sets of 3, petaloid or chaffy, mostly connate at base; both septal and tepalar nectaries commonly present; stamens usually 6 in 2 cycles, or the inner set staminodial or obsolete; filaments borne on the base of the perianth; ovary inferior, trilocular with axile placentation; styles or stigmas distinct; ovules mostly 2 per locule; fr mostly capsular; embryo small, with subterminal plumule and broad, lateral cotyledon, axially embedded in the very hard endosperm; twining-climbing or seldom erect herbs from a fleshy-thickened rhizome, or much more often from a large basal "tuber" of complex structure; lvs alternate or sometimes opposite or whorled, generally with a distinct blade and petiole, the blade broad, entire or less often palmately lobed or cleft or even compound, commonly with 3–13 "parallel," curved-convergent main veins and a network of smaller veins; vessels generally present in all vegetative organs; fls small, variously in racemes, spikes, or panicles. 6 genera, all but Dioscorea small.

Herbs twining or woody vines, rarely erect, small herbs. Rootstock rhizomatous or tuberous. Stem twining to left or right, pubescent or glabrous, sometimes prickly. Leaves alternate or opposite, petiolate, simple or palmately compound, basal veins 3--13, interstitial veins reticulate; leaflets of palmately compound leaves often ovate or lanceolate. Flowers usually unisexual (when plants dioecious, rarely monoecious), sometimes bisexual, solitary, clustered, or in cymules, these in a spike, raceme, or thyrse, these sometimes grouped into panicles. Male flowers: perianth lobes 6, in 2 whorls, basally connate or free; stamens 6, sometimes 3 reduced to staminodes or absent, inserted on perianth or receptacle; ovary rudimentary or absent. Female flowers: similar to male ones; staminodes 3, 6, or absent; ovary inferior, 3-loculed, ovules usually 2 per locule (more than 2 in a few small genera), placentation axile; styles 3, free. Fruit a capsule, berry, or samara. Seeds with a membranous wing or not; endosperm present; embryo small.

Perianth segments biseriate, usually united basally Stamens (3, 4) 6 Leaves alternate or opposite, often ovate-cordate, but sometimes with 3–7 digitate leaflets Flowers bisexual or unisexual, the latter usually dioecious Twining herbs with annual stems arising from tubers or rhizomes, rarely stems self-supporting Ovary inferior, rarely semi-inferior or superior, (1)3-locular Fruit a dehiscent capsule, samara or berry Stamens (3, 4) 6 Leaves alternate or opposite, often ovate-cordate, but sometimes with 3–7 digitate leaflets Flowers bisexual or unisexual, the latter usually dioecious Twining herbs with annual stems arising from tubers or rhizomes, rarely stems self-supporting Ovary inferior, rarely semi-inferior or superior, (1)3-locular Fruit a dehiscent capsule, samara or berry