843 
DIOSCOREA. 
gular, three-celled, three-valved. Seeds: in pairs, com- 
prefled, girt with a large membranous border .—EJfential 
CharaElcr. Male. Calyx, fix-parted ; corolla, none. Fe¬ 
male. Calyx, fix-parted; corolla, none; ftyles three; 
capfule three-celled, comprefled; feeds two, membrana¬ 
ceous. 
Species, i. Diofcorea pentaphylla, or five-fingered di- 
ofcorea : leaves digitate. Root very large and thick ; 
(talks fpiny, (lender; leaves quinate, flat, fmooth, thin, 
on petioles (triated within ; the midrib puts out feveral 
tranfverfe nerves, and thefe others covering the back 
as it were with a net; flowers firft yellow, then turning 
blackifh. Native of the Eaft Indies and the Society Ifles. 
2. Diofcorea triphylla, or three-fingered diofcorea: 
leaves ternate. This is very nearly allied to the forego¬ 
ing, and it may be doubted whether it be a diftinCt (pe- 
cies. The leaves are above dufky green, beneath fmooth 
and fhining, with whitifli prominent nerves, on long pe¬ 
tioles. Seeds in pairs, femi-elliptic, about an inch long, 
of a cinnamon colour. Native of Malabar. 
3. Diofcorea trifida, or trifid diofcorea: leaves cor¬ 
date, trifid. Native of Surinam. 
4. Diofcorea aculeata, or prickly diofcorea: leaves 
cordate ; (lent prickly, bulb-bearing. Native of Mala¬ 
bar and Cochin-china. 
5. Diofcorea alata, or wing-ftalked diofcorea : leaves 
cordate ; flem winged, bulb-bearing. Root a foot or 
more long, as big as a man’s leg or thigh, brown on the 
outfide ; within white or reddifh purple, vifeid, but when 
boiled very mealy. Stalk the bignefs of a goofe-quili, 
fquare, with a thin reddifh membrane at each corner, 
winding itfelf round poles nine or ten feet high, and put¬ 
ting out leaves at every three inches diftance, oppofite, 
on fquare winged footflalks two inches long ; leaves two 
inches and a half long, an inch and three quarters broad 
at the bafe, aJmoft heart-fhaped, pointed, yellowifh green, 
having many ribs arifing from the end of the footftalk 
with tranfverfe ones between ; peduncles axillary an inch 
or more in length, with fmall flowers of a yellowifh green 
colour. Native both of the Eaft and Weft Indies, and 
cultivated there for food as well as the fixth and feventh 
fpecies. This, indeed, has a better claim, as Forfter 
obferves, to the name of fativa than the feventh ; for it 
is univerfally cultivated in the Eaft and Weft Indies, in 
Africa, and in all the iflands of the Southern Ocean, 
within the torrid zone, and even as far as New Zealand. 
The roots are frequently three feet long, and weigh thirty 
pounds. In all the iflands of the South Sea, this yam is 
known by the Malay name vfi or ubi. The Portuguefe 
call this root inhame , hence the French ignanie, and our 
yam. Cultivated here in 1739 by Mr. Miller. 
6. Diofcorea bulbifera, or bulbed diofcorea: leaves 
cordate ; ftem even, bulb-bearing. Stalks (lender, fome- 
what woody, twining round each other. The leaves 
have many nerves and are acuminate. From the axils 
grow tubers which take root. Native of both Eaft and 
Weft Indies, and the iflands of the South Seas. Mr. 
Miller calls this the yam , and quotes the fynonynte of 
Sloane, with winged ftalks, whereas the (talks of this 
fpecies are even. 
7. Diofcorea fativa, or cultivated diofcorea, or yam : 
leaves cordate, alternate; ftem even, round. This has 
(lender ftalks, not winged, but round, climbing to the 
height of eighteen or twenty feet. The leaves have five 
longitudinal veins, which arife from the footftalks, and 
diverge towards the fides, but meet again at the point; 
they (land upon pretty long footftalks, and from the bafe 
of thefe arife the branching fpikes of flowers, which are 
fmall and have no beauty. Root a foot broad and flat¬ 
ter than in No. 5. almoft palmated like forne orchifes, 
dirty brown on the outfide. If it be Sloane’s plant, it 
is the negro-country yam, which he fays is much planted 
in Jam ica. Browne calls it the wild yam, (if it be his 
third fpecies, and not rather his firft,) and fays that it 
is not put to any ufe in Jamaica. lie refers to fagopyrum 
fcandens, &c. of Sloane, 138. There is much confufion 
in the fynonymes. It is a native of the Eaft and Weft 
Indies, and'Japan. 
.The yam is largely cultivated for food in Africa and 
the Eaft and Weft Indies, efpecially in the latter for the 
negroes. The roots grow to a great fize, are mealy, and 
efteemed to be eafy ofdigeftion ; they are palatable, and 
not inferior to any roots now in ufe, either for delicacy 
of flavour or nutriment. They are eaten inftead of bread, 
either roafted on the embers or boiled ; the flour is alfo 
made into bread and puddings. In Otaheite they make 
a did), which they efteern very delicious, from the roots 
of the yam, with the kernel of the cocoa-nut feraped, 
and the pulp of the mufa or banana. The juice of yam- 
roots frefli is acrid, and excites an itching on the (kin* 
There are many varieties of thefe roots, fome fpreading 
out like the fingers, others twifted like a ferpent, others 
again very fmall, fcarcely weighing more tjian a pound, 
with a whitifli afli-coloured bark, whereas the bark is 
commonly black. The flefli of the yam is white or pur. 
plifti, and vifeid, but becomes farinaceous or mealy when 
drefied. The varieties above-mentioned occurred to our 
circumnavigators in the ifiand of Otaheite, and belong 
rather to the fifth fpecies: there are dcubtlefs many va¬ 
rieties of a plant fo generally cultivated. 
8. Diofcorea villofa, or hairy diofcorea: leaves cor¬ 
date, alternate, and oppofite ; ftem even. This has 
broad, round, heart-fhaped, leaves, which end in acute 
points; they have many longitudinal veins, which arife 
from the footftulk, and diverge to the fide, but after¬ 
wards join at the point. The flowers come out on long 
loofe firings, on fhort pedicels. Native of Florida and 
Maryland. 
9. Diofcorea oppofitifolia, or oppofite-leaved diofco¬ 
rea : leaves oppofite, ovate,, acuminate. This has the 
appearance of a fmilax. Stem round, woody, twining, 
unarmed. Miller feems to confound it with the fore¬ 
going. Native of the Eaft Indies, Japan, and Cochin- 
china, where the roots are preferred to all others. Lou- 
rciro doubts whether this be different from the twelfth. 
10. Diofcorea feptemloba, or feven-lobed diofcorea: 
leaves cordate, feven-lobed, feven nerved, n. Diofco¬ 
rea quinqueloba, or five-lobed diofcorea : leaves cordate, 
five-lobed, nine-nerved. 12. Diofcorea Japonica, or Ja¬ 
pan diofcorea: leaves cordate, acuminate, nine-nerved. 
Natives of Japan. 
13. Diofcorea haftata, or fpear-leaved diofcorea: leaves 
haftate ; ftem even ; racemes very long. This differs from 
the feventh in the fliape of the leaves ; thefe having two 
round ears at their bafe, but the middle extends to an 
acute point, like a halbert. The bunches of flowers are 
longer, and loofer than thofe of the feventh fort. 
14. Diofcorea eburina, or ivory diofcorea: leaves heart- 
fhaped, feven-nerved, alternate; flowers hermaphrodite, 
in Ample long racemes. Stem fltrubby, unarmed, long, 
twining; root vertical, confiding of one or two tubers, 
three feet long, round, regular, fharpiflt, curved a little, 
in fliape and whitenefs refembling elephant's teeth, 
whence the vernacular name khoai vga, and the trivial 
eburina. 
15. Diofcorea cirrofa, or curled diofcorea: leaves 
ovate-lanceolate, three-nerved ; flowers hermaphrodite, 
three-ftamened ; ftem cirrofe. Stem fltrubby, long, (len¬ 
der, climbing. The root is a middle-fized irregular tu¬ 
ber. The capfule is that of diofcorea, but it differs in 
feveral other characters. This and the preceding are 
natives of Cochin-china. 
Propagation and Culture. Thefe plants may be propa¬ 
gated by laying their branches into the ground, where 
in about three months they will put out roots, and may 
then be taken from the old plants, and put into feparate 
pots, which fltould be plunged into the tan-bed in the 
ftove. During winter they (hould have little watery 
