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Order CLVIII. POLYGONACEJE. The Buck-wheat Tribe. 
PoLYGONEJE, Juss. Gen. 82. (1789); R. Brown Prodr. 418. (1810); Lindl. S7jnops. 209. 
(1829) ; Bentham in Linn. Trans, ined. (1836). 
Essential Character. — Calyx divided, inferior, imbricated in aestivation. Stamens 
definite, inserted in the bottom of the calyx ; anthers dehiscing lengthwise. Ovary supe- 
rior, with a single erect ovule ; styles or stigmas several. Nut usually triangular, naked, or 
protected by the calyx. Seed with farinaceous albumen, rarely with scarcely any ; 
embryo inverted, generally on one side ; plumule inconspicuous ; radicle at the end remote 
from the hilum. — Herbaceous plants, rarely shrubs. Leaves alternate, their stipules cohe- 
ring round the stem in the form of an ochrea; when young, rolled backwards. Flowers 
occasionally unisexual, often in racemes. 
Affinities. Brown remarks, that “ the erect ovulum with a superior ra- 
dicle together afford the most important mark of distinction between Polygo- 
naceae and Chenopodiacese, a character which obtains even in the genus Erio- 
gonum, in which there is no petiolar sheath, and scarcely any albumen, the 
little that exists being fleshy.” Generally speaking, however, the cohesion of 
the scarious stipules into a sheath, technically called an ochrea, or boot, is suf- 
ficient to distinguish Polygonaceae from all other plants. Bentham admits two 
Tribes, Polygonaceae which have loose flowers and ochreae ; and Eriogoneae 
which have flowers in involucres and usually no stipules. 
Geography. There are few parts of the world that do not acknowledge 
the presence of plants of this order. In Europe, Africa, North America, and 
Asia, they fill the ditches, hedges, and waste grounds, in the form of Docks 
and Persicarias ; the fields, mountains, and heaths, as Sorrels and trailing or 
twining Polygonums ; in South America and the West Indies they take 
the form of Coccolobas or sea- side grapes ; in the Levant, of Rhubarbs ; 
and even in the desolate regions of the North Pole they are found in the shape 
of Oxyria. 
Properties. Sorrel on the one hand, and Rhubarb on the other, may 
be taken as the representatives of the general qualities of this order. Wliile 
the leaves and young shoots are acid and agreeable, the roots are universally 
nauseous and purgative. To these two qualities is to be superadded a third, 
that of astringency, which is found in a greater or less degree in the whole 
order, but which becomes in Coccoloba uvifera so powerful as to rival gum 
Kino in its effects. Some of the Polygonums are extremely acrid, as the P. Hy- 
dropiper, which is said to blister the skin. There is a species of Polygonum, 
called Cataya in the language of the Brazilian Indians, an infusion of the ashes 
of which is used to purify and condense the juice of the sugar-cane. It has a very 
bitter peppery taste, and is employed on the Rio St. Francisco with advantage 
in the disease called O Largo, which is an enlargement of the colon, caused by 
debility. Pr. Max. Trav. 71. The stem of the Rheum has been supposed to 
contain a peculiar acid called the rheumic, but this is now known to be the 
oxalic. Turner, 641. Rumex acetosa contains pure oxalic acid. 623. 
The principle in which the active property of Rhubarb exists is supposed to be 
a peculiar chemical substance called Rhubarbarin. Ibid. 701. Some informa- 
tion may be found upon the Rhubarbs of India in the Trans, of the Med. and 
Phys. Soc. of Calcutta, 3. 438. by Royle ; but nothing certain has been collected 
by him with regard to the plant producing the true officinal substance. Many spe- 
cies of Polygonum are used in dyeing. The seeds of P. fagopyrum or Buck- wheat 
and tataricum are used as food, for the sake of their mealy albumen ; those of 
P. aviculare are said to be powerfully emetic and purgative ; but this is doubted, 
by Meisner. Mon. 49. The seeds of Polygonum barbatum are used as me- 
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