Dioscorea sambiranensis R.Knuth

Wilkin, Paul, Hladik, Annette, Jeannoda, Vololoniaina & Weber, Odile, 2009, The threatened edible yams of the Dioscorea sambiranensis R. Knuth species complex (Dioscoreaceae): a new species and subspecies, Adansonia (3) 31 (2), pp. 249-266 : 260-261

4. Dioscorea sambiranensis R.Knuth

In Engler (ed.), Das Pflanzenreich 87 (4. 43): 353 (1924); Perrier de la Bâthie, Mémoires de la Société linnéenne de Normandie, Nouvelle Série, Section Botanique 1 (2): 20 (1928); Burkill & Perrier de la Bâthie in Humbert, Flore de Madagascar et des Comores, 44e famille: 52 (1950). — Type: Madagascar. Antsiranana Province, Ambanja

District, Vallée du Sambirano, Beangona, XII.1922, ♂

fl., Perrier de la Bâthie 15684 (holo-, B, not seen; iso-,

K! [K000098957], P! [P00442455-7]).

Dioscorea fimbriata Jum. & H.Perrier, Annales du Musée colonial de Marseille, série 2, 8: 425 (1910). — Types: Madagascar. Antsiranana Province, Ambanja District, Sambirano , VIII.1908, ♀ fr., Perrier de la Bâthie 8201 (syn-, P! [P00496536], K!) (mixed collection, see remarks below). — Sambirano, X.1912, Perrier de la Bâthie 8244 (syn-, P! [P00496538]).

DESCRIPTION

A twining vine to at least 10 m, sometimes very vigorous in humid forest habits, stems annual from a fleshy tuber.Tubers (according to Burkill & Perrier de la Bâthie 1950) one per rainy season, vertically oriented, divergent, to 2 m × 10-20 cm, cylindric or sometimes forming a spiral, epidermis thin, offwhite, parenchyma white, subtended by a crown buried at least 15 cm below the soil surface. Indumentum of 0.05-0.7 mm long, straight hairs, erect to appressed, slightly swollen and straw-yellow at the base, otherwise acuminate in outline, colourless, hairs appearing grey when dense and tomentose (for example on young growth and inflorescence apices and ovaries), usually present on veins only of leaf lower surface (though usually increasingly lax on secondary and tertiary veins), pedicels and tepal dorsal surfaces, less dense on stems, inflorescence axes and developing capsules, occasionally a few on leaf upper surface, all older parts glabrescent. Stem base not seen. Upper stems left-twining, terete or drying with a longitudinal groove, to 6 mm in diameter, sometimes drying with a deep longitudinal groove, unarmed, dull light brown, olive-brown to black-brown or russet brown when dry, when fresh green above, paler below. Leaves alternate, blade 35-152 × 25-173 mm when fully expanded, usually broadly ovate so to orbicular or broader than long, rarely ovate, chartaceous to thinly so, often thickly so in fruiting material, shiny bright green above, paler below, drying dull mid to dark olivegreen to grey-green, sometimes brown with age, margins entire; base cordate, sinus 5-44 mm deep, usually narrow, sometimes weakly hippocrepiform; apex rounded and acuminate to broadly deltoid, 12-17 × 7-18 mm, with a c. 3-8 × 1 mm long, narrowly deltoid, darker forerunner tip at the apex, one seen with inrolled margins; veins (5 or) 7 or 9 to the apex, with a smaller, often bifid, vein to each basal lobe, primary venation prominent on lower leaf blade surface, sides flattened and thus deeper than wide and oblong in cross-section; petiole 18-143 mm long, colour as stem, basal and apical pulvini darker, terete but deeply channeled on upper surface, wings absent; lateral nodal organs (“stipules” of Burkill 1960) c. 1-3 mm broad, (projections plus node to c. 8 mm in diam.), flat, semicircular to crescent-shaped, thick and firm, on node and petiole base; cataphylls unknown (stem base not seen); bulbils not present. Inflorescences usually simple, pendent, axes and flowers green or yellow-green, usually with some red or purple pigmentation except towards the margins, scent not recorded. Male inflorescences 1 or 2 per axil, racemose, rarely compound, peduncle 3-42 mm long, axis 32-332 × 0.4 -2.2 mm, flattened, ridged and angled colour as stem; nodes 3-8 mm apart, irregularly spaced; cymules 1 or sometimes apparently 2 per node (probably due to very short basal cymule branches), bearing up to 12 green flowers, sometimes with a reddish or purplish hue, where 2 cymules one inserted above the other, cymule primary branch absent or to 1.7(-3.8) mm long and stout in some older cymules; cymule bracts 0.9-2.7 × 0.3-1.1 mm, ovate to elliptic, narrowly so or lanceolate, membranous with a thick opaque midrib, apex acute to acuminate; female inflorescences 19-137 mm long, on a 9-58 mm long peduncle, simple, spicate, axis colour as stem. Male flowers on pedicels 1.2-8.3(-13) × 0.2-0.4 mm, very slender in appearance, filiform, angled, only broadened immediately under flower; floral bracts at pedicel bases, 0.6-1.3 × 0.2-0.6 mm, narrowly ovate to lanceolate, like cymule bracts but smaller, decreasing in size towards cymule apex; tepal whorls undifferentiated to weakly differentiated (outer narrower and more acute), inserted on a 0.6-1.1 mm in diameter, ± flat, discoid torus, tepals 6, 0.6-1.5 × 0.5-1.0 mm, free, spreading to ascending, ovate or elliptic to narrowly to broadly so or ovate-oblong, thickly membranous, apex acute to obtuse, rarely short-acuminate; stamens in 2 whorls of 3, filaments erect, 0.05-0.25 mm long, anthers 0.15-0.3 × 0.1-0.25 mm, oblong to elliptic-oblong in outline, dorsifixed,yellow; pistillode 3-lobed, c. 0.1mm long, in a depression surrounded by a raised annulus in torus centre or with lacunae between pistillode lobes. Female flowers sessile, floral bracts 1.1-3.3 × 0.3- 1.4 mm, linear to ovate, apex acuminate, bracteole if present like bract but smaller, inserted at 90° to it, c. 1 mm apart in immature fruit; ovary c. 3.3-5.9 mm long, 3-angled, narrowly oblong to elliptic in outline, sometimes with a few flat, fleshy, rounded projections (membranous when dry) on the margins even when barely expanded; tepal whorls undifferentiated, inserted on a flat, discoid torus 0.5-1.0 mm in diameter, tepals 6, 0.9-1.6 × 0.7-1.0 mm, ovate to broadly so or ovate-oblong, chartaceous,apex acute to obtuse;staminodia 6, 0.1-0.15 mm long, substaminiform, 0.2-0.3 mm wide at antheriform apex; styles 3, 0.25-0.35 mm long, centrally fused at base, free part stout, spreading, stigmatic region bifid, lobes c. 0.2 mm long, spreading at c. 90° to each other (i.e. Y-shaped). Capsule 22-35 × 13-18 mm, patent to axis to ascending at c. 90°-30° to axis at dehiscence on a 2.3-7.7 × 1.2-1.7 mm, weakly clavate stipe, oblong-oblanceolate or oblong-obovate to oblong or elliptic in outline, green or yellow-green to purple or brown-hued, base obtuse to cuneate, apex truncate to broadly acute or rounded, bearing floral remains, axis and margin with dense to lax fleshy, rounded, sinuate projections (membranous when dry) present at maturity, in immature capsules small sinuate lobes on margins, axis undulate; tepals persistent at capsule apex until capsule fully expanded; capsule dehiscing almost to base to expose seed, operculum breaking away still bearing sinuate lobes, capsule dark to pale brown,lobes rigid,2-layered (sinuate lobes part of thin outer layer), inner layer thicker and firmer, smooth inside.Seed winged at base only, 6.2-9.4 × 3.7-5.9 mm excluding wing, flattened lenticular-reniform, dull matt brown, wing 8.8-14 × 5.1-7.1 mm, oblong to weakly deltoid-oblong, apex truncate to obtuse, membranous, translucent golden-brown.