DIOSCOREA 



DIOSCOREA 



1013 



and sometimes bearing tubers in the axils: Ivs. broad, 

 ribbed and netted-veined, petiolate, alternate or oppo- 

 site, 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 hand- 

 some colored foliage and are 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. 



A. Sts. strongly winged. 



alata, Linn. Fig. 1269. St. 4-winged or angular: Ivs. 

 opposite, cordate-oblong, or cordate-ovate, with a 

 deep, basal sinus, glabrous, devoid of pellucid dots, 

 7-nerved (sometimes 9-nerved), with the outer pair 

 united: staminate spikes compound, special ones 

 whorled, short, flexuose; pistillate spikes simple; fls. 

 distant, anthers subglobose, about as long as the 

 filament: caps, leathery, elliptical. India and the South 

 Sea Isls. Widely cult, in the tropics under many 

 vernacular names. Tubers reach a length of 6-8 ft., 

 and sometimes weigh 100 Ibs.; edible. The roots con- 

 tinue to grow for years. Variable. 



AA. Sts. terete (cylindrical) . 

 B. Lvs. plain green. 



Batatas, Decne. (D. divaricata, Auth., not Blanco). 

 YAM. CHINESE YAM. CHINESE POTATO. CINNAMON- 

 VINE. Tall climbing (10-30 ft.), the Ivs. 7-9-ribbed, cor- 

 date-ovate and shining, short-petioled, bearing small 

 clusters of cinnamon-scented white fls. in the axils : root- 

 tubers deep in the ground, 2-3 ft. long, usually larger 

 at the lower end. Philippines. 

 F.S. 10:971. R.H. 1854, pp. 

 247, 451, 452. This is often 

 grown in the tropics for its 

 edible tubers, which, however, 

 are difficult to dig. In this 

 country the word yam is com- 

 monly applied to a tribe of 

 sweet potatoes (see Sweet 

 Potato). The 

 yam is hardy. 

 The root will 

 remain in the 

 ground over 

 winter in New 

 York, and send 

 up handsome 

 tall twining 

 shoots in the 

 spring. The 

 plant bears lit- 

 tle tubers in 

 the If.-axils, 

 and these are 

 usually planted 

 to produce the 

 cinnamon vine; 

 but it is not 

 until the sec- 

 ond year that 

 plants grown 



1269. Dioscorea alata, showing foliage from these 



and a small tuber. tubercles pro- 



duce the large or full-grown yams. A form with 

 short and potato-like tubers is D. Decaisnedna, Carr. 

 (R.H. 1865:110). A vine widely cult, since 1910 

 under the name air potato" or "giant yam vine" has 

 large potato-shaped bitter tubers. Its identity is in 

 doubt. It is not D. divaricata, under which name it 

 was intro. from Hawaii, nor D. bulbifera, which has 

 angular and edible aerial tubers. In order to distin- 



1270. Air potato. Aerial tuber of Dioscorea bulbif era. ( X J4) 



guish it from the latter, it has recently been called the 

 'Hawaiian bitter yam." The yampi is apparently a 

 form of D. alata. This and other forms of this species 

 are grown in Fla. and La., for the excellent edible 

 tubers, which compare favorably with the potato. 



bulbifera, Linn. AIR POTATO. Fig. 1270. Tall- 

 climbing: Ivs. alternate, cordate-ovate and cuspidate, 

 7-9-nerved, the stalks longer than the blade: fls. in 

 long, lax, drooping, axillary racemes. Trop. Asia. 

 G.C. III. 52:313. Somewhat cult. S. as an oddity 

 and for the very large angular axillary tubers (which 

 vary greatly in size and shape). These tubers some- 

 times weigh several pounds. They are palatable and 

 potato-like in flavor. The root-tubers are usually 

 small or even none. 



BB. Lvs. variously marked and colored, at least beneath 

 (greenhouse "foliage plants"). 



discolor, Hort. Lvs. large, cordate-ovate, cuspidate, 

 with several shades of green, white-banded along the 

 midrib and purplish beneath: fls. greenish and incon- 

 spicuous: root tuberous. S. Amer. Lowe 54. F.W. 

 1877:353. Useful for the conservatory. Suggestive 

 of Cissus discolor. 



multicolor, Lind. & Andre". Probably only a form of 

 the last: Ivs. variously marked and blotched and veined 

 with silvery white, red, green and salmon. S. Amer. 

 I.H. 18:53. Very decorative glasshouse plant of 

 several well-marked forms (some of them under Latin 

 names). 



D. villdsa, 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 has recognized 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, %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: Ivs. 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, %-l H in. long. Woods and banks, N. C. 

 to Fla., La., Mo. and Ark. D. glaitca, Muhl. Rhizomes %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: Ivs. 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 infl. solitary in all axils, paniculate; pistillate infl. 

 few-fld. : fr. to 1)4 in- long. Pa. southward along the mts. to 

 S. C. and west to E. Mo. D. paniculdta, Michx. Rhizomes long 

 and slender, simple or rarely forked, less than %in. diam., with a 

 few short thinner laterals: st. 3-14 ft., flexuose, glabrous: Ivs. 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. glabrifdlia, Bartlett, has glabrous Ivs. Mass, to Minn., 

 south to Texas in the middle region. D. hirticaitlis, Bartlett. 

 Rhizome less than %in. diam., simple or rarely forked, nearly 



