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This species is accepted, and its native range is N. & E. Madagascar.
A specimen from Kew's Herbarium


Wilkin, P., Andrianantenaina, W.P. et al. (2008). The species of Dioscorea L. (Dioscoreaceae) from Madagascar with campanulate tori, including a new species from Eastern Madagascar. Kew Bulletin 63: 583.

Data Deficient (DD) (IUCN 2001). However, this species is potentially threatened; for example, there is significant disturbance for shifting cultivation at Mt Vatovavy. Four populations have been encountered, although the mixed nature of Perrier 8201 (see Notes below) and the absence of a more recent collection from Manongarivo suggests that the latter locality may be an error.
Three localities in Fianarantsoa Province (Manombo near Farafangana, Mt Vatovavy near Kianjavato and Ifanadiana) and in Sambirano in the North (the type of D. knuthii).
Found in humid forest, often on forest margins or in areas of disturbance; c. 0 – 200 m a.s.l.
Morphology General Habit
A twining vine to at least 5 m, stems annual from a fleshy tuber
Morphology General Indumentum
Indumentum of colourless, unmodified, simple hairs, 0.1 – 0.5 mm long, quite dense and often appressed on pedicel, ovary and outer tepals of female flower, sparse on female floral bracts and inner tepals, male floral bracts and tepals and very sparse on inflorescence axes, largely caducous Stems left-twining, terete, to c. 3 mm in diam., thicker with small spines or irregularly toothed, fleshy to firm ridges towards the base, with faint longitudinal ridges above, otherwise unarmed, pale green, sometimes with dark purple pigmentation towards base, often drying dark brown
Morphology Leaves
Leaves alternate, blade 4 – 12.2 × 1.2 – 6 cm (larger leaves seen during fieldwork), elliptic to lanceolate or narrowly ovate, thickly chartaceous, dark green above, pale below and on forerunner tip, red in early development, shiny on both surfaces when immature, drying very dark brown above, paler below, primary and secondary venation prominent on upper and lower leaf blade surfaces; margins entire, base of vegetative shoot leaves cordate to shallowly so, sometimes weakly auriculate, reproductive shoot leaves rounded to truncate, sinus to 11 mm deep, apex acuminate, gradually to abruptly differentiated from blade, 6 – 11 mm long with a 1 – 3 mm long, deltoid, brown forerunner tip, veins 3 – 5 to the apex, with a smaller pair to the base; petiole 7 – 57 mm long, pale green, pulvinii dark purple, sometimes drying reddish-brown, strongly channelled on upper surface; lateral nodal spines present as small recurved projections to c. 2 mm long on amplexicaul petiole bases
Morphology Leaves Cataphylls
Cataphylls and bulbils not present
Morphology Reproductive morphology Flowers
Male flowers (sub)sessile, orientated at 15 – 60° to axis, not scented, ovoid-cylindric in bud, pedicels (where present) to 0.6 mm long, obdeltoid in outline, floral bract 0.4 – 1.6 × 0.5 – 1 mm, ovate to broadly so, especially broad at extreme base, where it clasps partial inflorescence axis, apices acute to acuminate, membranous with a thickened midrib and base, purple at base, clear green towards apex before anthesis, later browner and chartaceous towards base, membranous at apex, bracteoles 1 or 2, like bracts but smaller; tepal whorls differentiated only by slightly greater width of three tepals of outer whorl, free or slightly fused at base, inserted on an ovoid, weakly urceolate torus 1 – 1.5 × 0.7 – 1.2 mm, clear green and fleshy, especially towards base; tepals 0.6 – 1.1 × 0.3 – 0.7 mm, variable in shape, lanceolate to ovate, ovate-oblong or broadly ovate, thinly chartaceous to membranous, erect in bud, strongly recurved at or after anthesis, often purple-hued, apex obtuse to acuminate; stamens erect, exserted, filaments 0.4 – 1 mm long, free, filiform, inserted at pistillode base or on pistillode, clear green; anthers 0.25 – 0.5 × 0.15 – 0.2 mm, oblong or elliptic-oblong, basifixed, pale yellow; pistillode 0.2 – 0.4 mm long, fleshy, 3-lobed at apex Female flowers not scented; floral bract clasping pedicel base, to 1.8 mm long, ovate, acuminate, with a narrower bracteole, both usually purple; pedicel (1.5 –) 3 – 7 mm long, stout, terete, colour as rachis; ovary 4 – 10 mm long, 3-angled, narrowly oblong to narrowly oblong-elliptic, base and apex acute, axis and angles with dense dark purple mottling, wings glossy green; torus 0.4 – 0.9 × 1 – 1.6 mm, shallowly infundibular, floral stipe absent; tepals 1.8 – 2.7 × 0.6 – 1.3 mm, lanceolate to ovate, fused at base, the two whorls scarcely or not differentiated, distally recurved, sometimes becoming more erect after the stigma has ceased to be receptive, purple in bud, fading to pink or dull olive green; staminodia 6, in a single whorl around the style bases, 0.2 – 0.3 mm long, staminiform, pale green; styles 3, fused at base only, 0.8 – 1.2 mm long, erect, bifid towards apex with the stigmatic lobes divergent, pale green
Morphology Reproductive morphology Fruits
Capsule 32 – 55 × 15 – 25 mm, ascending at c. 60° to axis at dehiscence on a 3.3 – 6.2 mm long, recurved, clavate in outline, 3-angled pedicel, oblong-oblanceolate to narrowly suboblong or narrowly obovate, base obtuse to acute, apex bluntly acute, styles persistent as an apiculus on each lobe of capsule, apical part only opening to expose seed, wing basal and therefore concealed, dark brown with paler and greyish flecking outside, tan inside, appearing 2-layered
Morphology Reproductive morphology Inflorescences
Inflorescences to c. 50 cm long, lax, axis stout, laterally flattened and with 2 longitudinal ridges which appear acute in cross-section, green, sometimes with dull purple mottling, mottling dense on floral bracts and pedicels Male inflorescences on main stems simple, spicate, 1 – 2 per axil, those on terminal shoots nodes with leaves highly reduced or absent so compound, primary axis to c. 30 cm × 0.3 – 0.7 mm, with up to 5 partial inflorescences per node, both primary and partial inflorescence axes longitudinally ridged and winged; simple inflorescence axes to c. 50 cm long including 1.4 – 4 cm long peduncle, compound inflorescence partial inflorescences 2.5 – 10.5 cm long (including 3 – 15 mm long peduncle), slightly flexuous, in both flowers 4 – 7 mm apart, usually solitary, rarely in pairs Female inflorescences to c. 50 cm long, 1 per axil, racemose, flowers pendent in bud, spreading at floral opening, patent to inflorescence rachis when receptive
Morphology Reproductive morphology Seeds
Seed winged at base only, 9 – 12 × 6 – 8 mm excluding wing, flattened-reniform, dull dark brown, wing 13 – 24 × 6 – 9 mm, lanceolate to narrowly oblong-elliptic, apex obtuse, membranous, chestnut-brown with paler flecking.
Determining the correct name for this species was complicated by the existence of the name Dioscorea knuthii H. Perrier. The problem originates with the specimen Perrier 8201. It is a mixed collection: female D. sambiranensis R. Knuth and a second glabrous taxon with sessile male flowers. They were described together as D. fimbriata with Perrier 8244 by Jumelle & Perrier (1910). The mistake was picked up by Perrier (1928), who placed D. fimbriata (pro parte) in synonymy with D. sambiranensis R. Knuth. He also described the second part of the specimen (Perrier 8201bis) as D. knuthi (sic) there. This was reduced to synonymy with D. tsaratananensis H. Perrier in Burkill & Perrier (1950) but this is manifestly incorrect because Perrier 8201bis has (sub)sessile flowers, while D. tsarataranensis has a pedicel not less than 3.6 mm long. The pedicel is both described and illustrated in the Flora treatment. Thus this name is applicable to the taxon under discussion. D. madecassa H. Perrier, Mem. Soc. Linn. Normandie 1: 24 (1928) was selected by the authors over D. knuthii H. Perrier, Mem. Soc. Linn. Normandie 1: 32 (1928) as the name for the combined taxon because although they have equal priority under article 11.5 of the St. Louis Code of the ICBN the former is in current active use in e.g. Burkill & Perrier (1950) while the latter was placed in synonymy. The plants photographed on the “Oviala” project website ( under the vernacular name Vorozy appear to belong to this species and/or Dioscorea seriflora.
Madagascar, Fianarantsoa Prefecture, environs de Farafangana, ♂ fl. May 1912, Perrier 12614 (holotype P!; isotype P!).
Vegetative Multiplication Tubers
Tubers annually replaced, one per growing season, usually two present during flowering, deeply buried (c. 1.5 m), narrowly claviform, to c. 3 m × 10 cm thick (according to Tanala guide at Vatovavy); more frequently less deeply buried and c. 50 × 1 cm at crown and 5 cm towards apex, lobed or branched, especially towards apex, epidermis yellowish, parenchyma white, mucilaginous, crown not clearly differentiated from tuber apex
Karatana (Tanala, Vatovavy), Oviala (a generic name for edible yams, Manombo).

Tuber edible (cooked).

Native to:


Dioscorea madecassa H.Perrier appears in other Kew resources:

Date Reference Identified As Barcode Type Status
Perrier de la Bâthie, J.M.H.A. [12614], Madagascar K000098651 Unknown type material
Wilkin, P. [[947A]], United Kingdom K001148435
Wilkin, P. [947], United Kingdom K001148437
Chase [21047], Madagascar K000728352
Wilkin, P. [[947]], United Kingdom K001148433
Wilkin, P. [[947A]], United Kingdom K001148434
Wilkin, P. [947 A], United Kingdom K001148438
Wilkin, P. [947], United Kingdom K001148440
Ranarivelo, T. [387], Madagascar K000728354
Andrianantenaina, W. [AWP 76], Madagascar K001171813
Wilkin, P. [947], United Kingdom K001148436
Ranarivelo, T. [387], Madagascar K000728353
Wilkin, P. [947 A], United Kingdom K001148439
Wilkin, P [947], Madagascar Dioscorea karatana K000098878 isotype
Wilkin, P [947], Madagascar Dioscorea karatana K000098879 isotype
Rajaonah, M.T. [MT 297], Madagascar Dioscorea karatana K001148457

First published in Mém. Soc. Linn. Normandie, Bot. 1(1): 24 (1928)

Accepted by

  • Govaerts, R. (2000). World Checklist of Seed Plants Database in ACCESS D: 1-30141.
  • Govaerts, R., Wilkin, P. & Saunders, R.M.K. (2007). World Checklist of Dioscoreales. Yams and their allies: 1-65. The Board of Trustees of the Royal Botanic Gardens, Kew.
  • Wilkin, P., Andrianantenaina, W.P., Jeannoda, V. & Hladik, A. (2008 publ. 2009). The species of Dioscorea L. (Dioscoreaceae) from Madagascar with campanulate tori, including a new species from Eastern Madagascar Kew Bulletin 63: 583-600.

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© Copyright 2017 World Checklist of Selected Plant Families.

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Kew Names and Taxonomic Backbone
The International Plant Names Index and World Checklist of Selected Plant Families 2021. Published on the Internet at and
© Copyright 2017 International Plant Names Index and World Checklist of Selected Plant Families.