Dioscorea villosa |
Dioscorea polystachya |
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colic root, wild yam, yam root |
Chinese yam, cinnamon vine |
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Habit | Plants rhizomatous; rhizomes brownish, unbranched or highly branched, linear to irregularly contorted, 0.5–1.5 cm or more diam., nodes not articulate. | Plants tuberous; tubers 1–many, on long stalks and deeply buried, spindle-shaped. |
Stems | longitudinally grooved or sometimes narrowly winged, usually terete in cross section, 1–7 m, ± rigid proximally, or flexible, glabrous or rarely with sparse pubescence, wings when present less than 1 mm and stems polygonal. |
twining clockwise, unwinged, terete, climbing to 5 m, producing small bulbils (less than 2 cm diam.) in leaf axils. |
Leaves | alternate, subopposite, subverticillate, or in verticels of 3–7 proximally, due to suppression of proximal internodes (esp. |
alternate proximally, usually opposite distally, occasionally ternate, 3–9 × 3–11 cm; petiole as long as blade, base not clasping; blade 7(–9)-veined, hastate-cordate, glabrous, margins 3-lobed, basal lobes spreading, rounded to ± rhombic, median lobe deltate to ovate, apex acuminate or mucronate; primary veins 7(–9); basal leaves often less distinctly lobed or entire and ovate-cordate. |
Staminate flowers | perianth greenish white, appearing darker in some specimens due to presence of irregularly distributed tannin crystals, rotate-campanulate to funnelform, 1–2(–3) mm diam.; tepals ± glandular, ovate-elliptic, margins hyaline, apex rounded or acute; stamens in 2 subequal whorls, erect; anthers ca. ½ length of filaments, thecae distinct, widely spreading. |
perianth drying dark, tightly cup-shaped; tepals ovate, ca. 1 mm, margins hyaline, apex acute; fertile stamens 6; filaments connate basally; anthers as long as or longer than filaments, thecae distinct, weakly spreading. |
Pistillate flowers | perianth greenish white, rotate-campanulate, 2–4 mm wide; tepals as in staminate flowers; staminodes 6, differentiated into anthers and filaments, less than 1/2 length of fertile stamens. |
perianth as in staminate flowers; staminodes 6 in 2 subequal whorls, anthers and filaments more strongly differentiated in inner whorl, filaments less developed in outer whorl, all smaller than fertile stamens. |
Capsules | greenish gold, ovoid to obovoid to obreniform, 1–3 × 1–3.5 cm, varying continously in size, occasionally ± glaucous. |
not reflexed at maturity, broadly ovate, (1.2–)1.7–2 cm wide. |
Seeds | generally 2 per locule, rarely 1, 5–18 mm. |
winged all around. |
In | woodland understory), always alternate distally, 3–13 × 2–13 cm, ca. as long as wide; petiole ridged or narrowly winged, 3–14 cm, glabrous or puberulent at pulvinus, base not clasping; blade green to ± glaucous, (7–)9–11-veined, ovate-cordate, abaxial surface sometimes ± glandular, or sparsely or sometimes densely pubescent to glabrous, base with sinus rounded, acute, or ± truncate basally, margins entire or repand, apex acute to acuminate, occasionally mucronate. |
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Staminate | inflorescences solitary in leaf axils, rarely terminal, spicate or branched; cymes sessile, bearing 1–3 sessile flowers, braceolate, internodes between cymes 1–8 mm, bracteoles ca. 1 mm; rachis 2–30 cm, secondary axes to 15 cm, robust plants occasionally branched to third order, axes subtended by linear-lanceolate bracts 1–3 mm. |
inflorescences axillary, in fascicle of (1–)3–5 spikes, each spike shorter than 5 cm, or primary inflorescence axis elongate and bearing multiple fascicles; spikes bearing flowers singly, flowers bracteate, distributed along rachis in markedly zigzag pattern, internodes less than 2 mm. |
Pistillate | inflorescences solitary, 4–18-flowered, 4–20 cm, internodes 6–12 mm. |
inflorescences 1 per leaf axil, few-flowered, shorter than 5 cm, internodes between mature flowers greater than 1 cm. |
2n | = 20, 36, 54, 60. |
= 140. |
Dioscorea villosa |
Dioscorea polystachya |
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Phenology | Flowering mid spring–summer; fruiting late summer. | |
Habitat | Borders of bogs, swamps, marshes, river and lake margins, creek bottoms, sandy or rocky soils, moist or dry woods, hammocks, thickets, limestone or talus slopes, roadsides | Staminate plants flowering summer. Thickets, ravines, stream banks, creek bottoms, limesinks, granite outcrops, alluvial woods, roadsides, drainage canals, waste places, fence rows |
Elevation | 0–1500 m (0–4900 ft) | 0–500 m (0–1600 ft) |
Distribution |
AL; AR; CT; DC; DE; FL; GA; IA; IL; IN; KS; KY; LA; MA; MD; MI; MN; MO; MS; NC; NE; NJ; NY; OH; OK; PA; RI; SC; TN; TX; VA; VT; WI; WV; ON
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AL; AR; CT; DC; FL; GA; KY; MA; MD; MO; MS; NC; NJ; OH; PA; SC; TN; VA; WV; e Asia [Introduced in North America]
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Discussion | Dioscorea villosa is a highly polymorphic species, exhibiting complex patterns of variation across its geographic range. Characters that have been used previously to delineate taxonomic boundaries within this complex—pubescence, glaucousness, rhizome thickness and shape, length of internodes within the inflorescence, arrangement of proximal leaves, geometry of the stem, and fruit and seed size/shape—fail when individuals from all parts of the range and specimens representing both apical and basal portions of single stems can be examined. At its morphological extremes, D. villosa comprises 1) small vines with tightly congested inflorescences, winged stems, and variously pubescent leaves, occurring in bogs and branch swamps; and 2) robust plants, rigid at the base, the proximal leaves verticillate with large, glaucous blades, from the axils of which arise lax spikes or panicles, inhabiting rocky, upland woods and steep talus slopes. As one ascends from the Atlantic Coastal Plain through the Appalachians, continuing westward to the Great Lakes region, south to the Ozarks, and east to the branch swamps of Georgia, particular morphologies are associated with particular ecological conditions, independent of geography. As well as the morphological extremes, every intermediate condition of leaf, stem, and inflorescence architecture can be found, in all combinations, and variation may be encountered even within individual plants. What sort of genetic structure underlies these patterns of morphological diversity remains an open question. That there is a significant degree of genetic variability within the complex is evident from the chromosome counts thus far reported. Further research is needed to shed light on patterns of gene flow in the complex, and garden studies would be instructive as to the limits of individual plasticity. At present, I can find no natural gaps in the variation between the plants that have been called (albeit ambiguously; see H. H. Bartlett 1910) D. villosa and those called D. quaternata, and therefore I am treating the complex as a single species. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Dioscorea polystachya is native to eastern Asia, where it is cultivated for its edible tubers. In North America, it is planted as a garden ornamental and has become naturalized throughout much of the eastern United States. Only one pistillate specimen was encountered from the flora area, the plants apparently propagating vegetatively. Dioscorea polystachya is the earliest published name for this species. The name D. oppositifolia Linnaeus, which has been misapplied to this species, actually refers to an ovate-leaved species that is native to the Indian Subcontinent and is not found in the flora area. For a more detailed nomenclatural history of D. polystachya, see Ting C. T. and M. G. Gilbert (2000). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 26, p. 482. | FNA vol. 26, p. 483. |
Parent taxa | Dioscoreaceae > Dioscorea | Dioscoreaceae > Dioscorea |
Sibling taxa | ||
Synonyms | D. cliffortiana, D. glauca, D. hexaphylla, D. hirticaulis, D. longifolia, D. lloydiana, D. megaptera, D. paniculata, D. paniculata var. glabrifolia, D. pruinosa, D. quaternata, D. quaternata var. glauca, D. quinata, D. repanda, D. villosa var. glabra, D. villosa subsp. glabrifolia, D. villosa var. glabrifolia, D. villosa subsp. glauca, D. villosa subsp. hirticaulis, D. villosa var. hirticaulis, D. villosa subsp. paniculata, D. villosa subsp. quaternata, D. villosa var. vera, D. waltheri | D. batatas |
Name authority | Linnaeus: Sp. Pl. 2: 1032. (1753) | Turczaninow: Bull. Soc. Imp. Naturalistes Moscou 10(7): 158. (1837) |
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