|Standard Cyclopedia of Horticulture|
Dioscorea (Dioscorides, Greek naturalist of the first or second century of the Christian era). Dioscoreaceae. Twining herbs from tuberous or thickened rootstocks, grown as arbor vines or under glass for the foliage, and also for the edible rhizomes and aerial tubers.
Type genus of a small family (of about 9 genera) allied to Liliaceae. It contains more than 200 widely dispersed and confused species, most of them native to tropical regions. Sts. herbaceous and twining or long-procumbent, usually from a large tuberous root, and sometimes bearing tubers in the axils: lvs. broad, ribbed and netted-veined, petiolate, alternate or opposite, sometimes compound: fls. dioecious, small; calyx 6-parted; anthers 6; styles 3; ovary 3-loculed and calyx adherent to it: fr. a 3-winged caps.; seeds winged.— The great subterranean tubers of some species are eaten in the manner of potatoes. Some of the kinds have handsome colored foliage and arc good glasshouse subjects. Numbers of species are more or less cult. in different warm countries (see, for example, Paillieux & Bois, "Le Potager d'un Curieux," and for Japanese species Georgeson, A.G. 13:80); but it is not known that many of them have appeared in the U. S. The tuber- bearing species need to be worked over thoroughly from living plants. For an inquiry into the prehistoric cult, of dioscoreas in Amer., see Gray & Trumbull, Amer. Journ. Sci. 25:250.
All the species are of very easy cultivation from seeds or tubers or cuttings. The tubers keep a long time, like potatoes.
D. villosa. Linn., a native dioscorea, is offered. Bartlett has recently worked over the species native to the U. S. (Bull. 189. Bur. PI. Ind., U. S. Dept. of Agric., 1910) and baa recognised 5 species in the material formerly passing as D. villosa; and the name villosa itself he finds to be untenable because of the confusion attending it (a similar case lies with D. sativa, Linn., a name applied to oriental species). The 5 species are as follows: D. quaternata. Gmel. Rhizomes stout, ⅔ in. diam., straight or forked, with few or no lateral branches: sts. 3-8 ft. long, rigid and erect at base but requiring support above: lvs. mostly 5 and 6 at a node, alternate above, cordate, repand, green on both sides, glabrous: staminate fls. panicled, the clusters solitary in the axils; pistillate fls. few in the cluster: fr. variable, ⅖-1⅕ in. long. Woods and banks, N. C. to Fla., La., Mo. and Ark.—D. glauca, Muhl. Rhizomes ⅖ in. or more diam., often forked and with many short lateral branches (the source of the drug "dioscorea"): st. 3-10 ft. long, rigid and erect at base but requiring support above: lvs. in whorls of 5-7. the upper ones alternate, larger than in D. quaternata and less or not at all repand glabrous or hirtellous, glaucous at maturity: staminate inn. solitary in all axils, paniculate; pistillate infl. few-fld.: fr. to 1¼ in. long. Pa. southward along the mts. to 8. C. and west to E. Mo.—D. paniculata, Michx. Rhizomes long and slender, simple or rarely forked, less than ⅖ in. diam., with a few short thinner laterals: St. 3-14 ft., flexuose, glabrous: lvs. all alternate or nearly so. pubescent beneath: staminate infl. solitary in the upper axils; pistillate infl. densely many-fruited: fr. less than 1 in. Var. glabrifolia. Bartlett, has glabrous lvs. Mass, to Minn., south to Texas in the middle region.—D. hirticaulis, Bartlett. Rhizome less than ⅖ in. diam., simple or rarely forked, nearly striaght, with abort thin laterals: st. 3-10 ft., weak and flexuose, pubescent: lvs. all alternate (except perhaps at lowest node), grayish pubescent: staminate infl. solitary in upper axils, the upper ones paniculate; pistillate infl. with 1-4 frs., which are nearly 1 in. long. Carolinas and Ga. — D. floridana, Bartlett. Rhizomes undescribed: St. flexuose and twining: lvs. alternate, wholly glabrous, green above and paler beneath: staminate infl. paniculate, in the upper axils and also terminal ; pistillate infl. solitary, 5-7-fld. : fr. similar to those of D. paniculata, nearly 1 in. long, 8. C. to Fla.
Of the many names appearing in horticultural literature, the following are recent: D. argyraea, Hort. Lvs. with silver-gray angular patches along the main nerves. Colombia. Probably one of the D. discolor-multicolor group. — D. bicolor, Hort. Greenhouse climber, with ovate and cordate lvs., variegated above and deep purple beneath. G.W. 13, p. 254. Perhaps a garden form of some species, although there is a D. bicolor, Prain & Burkill described in a Bengal journal. - D. Fargesii, Franch. Twining, with spherical aerial tubers: lvs. of 3-5 parts or lfts., ternate or digitate, the parts oval or oval-lanceolate, more or less acuminate: female fls. in a very long cluster, sessile, subtended by lanceolate bracts; female fl. oblong, with 6 short segms. : subterranean tuber globular, said to be edible; plant produces aerial tubers. W. China. R.H. 1900, p. 685. — D. globosa, Roxbg. Cult. by Hindoos: tubers large, round and white: sts. 6-winged, prickly toward the root: lvs. sagittate-cordate, ensiform. 5-7-nerved. the long petiole 5-winged: staminate infl. long-pendulous and compound, and verticillate; pistillate infl. simple and erect in the axils, few-fld. India. This name is listed in Eu. — D. illuatr&ta, Hort., appears in European lists: lvs. satiny green with a central band of gray, transverse lines of white, and gray patches, under surface purple. Brazil. Probably one of the D. discolor group. — D. japonica, Thunb. St. slender, climbing 10-12 ft.: lvs. ovate with tapering apex and deeply cordate base, with some of the axils bearing small oblong tubers or bulbels: pistillate fls. small, white, racemose near the top of the plant: fr. triangular, winged: root 3-4 ft. long, 1-2 in. diam., often branched. Japan. Cult, forms have thicker and more condensed roots, and are eaten after the manner of potatoes. Offered abroad. — D. macroura. Harms. Lvs. simple, alternate, glabrous, stalked, cordate-orbicular, 1 ft. each way, undulate, with an apical cusp 1½-2 in. long: male fls. in a large panicle, the racemes reaching 2 ft., the fertile stamens 6 and very short. Upper Guinea (Trop. Afr.). — D. retiusa. Mast. Sts. slender, much twining, finely pubescent: lvs. alternate, compound; lfts. 5, stalked obovate, retuse, to 2 in. long, green and glabrous: male fls. few, in short-peduncled racemes; perianth- segms. oblong and connivent; fertile stamens 3 and staminodea 3. S. Afr. G.C. 1870: 1149. G.Z. 22, p. 242. L. H. B.
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- Standard Cyclopedia of Horticulture, by L. H. Bailey, MacMillan Co., 1963