Polygonum. CX. POLYGONACEiE. 473 



sports into many pleasing varieties with yellow and white, red and white, red 

 and yellow flowers. June — Sept. 



2. M. DicHOTOMA. Mexican Four-o'clock. — Fh. sessile, erect, axillary, soli- 

 tary. — % From Mexico. Stem 2f high, dichotomous, with yellow flowers, 

 opening at 4 o'clock like the former. July, Aug. 



3. M. LONGiFLORA. Long-floicBred Foxir-o'' clock. — hvs. pubescent ; jis. crowd- 

 ed ; tube of the cal. very long. — % Native of Mexico. Stem 2f high. Tube of 

 the calyx slender, hairy, twice as long as the leaves. Flowers white. Jn. — Sept. 



Order CX. POLYGONACEiE.— Buckwheats. 



Hf-?&s, rarely shrubs, with alternate leaves. (base of the leaf-stalks ; occasionally 0. 



Slip, of that remariiable kind called ochreag, cohering round the stem in the form of a sheath above the 



FiS. mosily jjerlect, and in racemes. 



Ca/.— Sepals united at base, imbricate in aestivation. 



Sea. tlefiniie, ins^erted on the calyx near the base. 



Ova. fee, with a single erect ovule. Slytes or stigmas several. 



Fr.— Achenium usually triangular. 



Sds.— Embryo -reneraily on one side of farinaceous albumen. 



Genera 29, species 490, widely diffused throughout the world. 



Properties.—The roots of these plants are nauseous and purgative. Rhubarb of the shops is the root 

 of sonif. unknown species of this order, native of Tartary. But the leaves and sta/ks of sorrel, the gar- 

 den rhubarb, <fec., are agreeably tart, and contain oxalic acid ; the_petioles of the latter, together with the 

 tarinaceous seeds of the buck- wheat, are well-known articles of food. 

 Conspectus of the Genera. 



< 6. Stigmas 3, multifid. 3 outer sepals smaller Rumex. 4 



( 6. Stamens 1 9. Stigmas multifid R/i'um. 1 



■^ mostly 5, united at base, persistent and enclosing the fruit Poljgonum. Z 



. Radical leaves rcniform, on long petioles Oxyria, 2 



1. RHEUM. 



Rha, the river Volga, on whose banks the plants are said to be native. 



Calyx colored, 6-sepaled, persistent; stamens 9 ; styles 3 ; stigmas 

 multifid, reflexed ; achenia 3-angled, the angles margined. — % Fls. 

 fasciculate., in racemose jpanicles. 



R. Rhaponticum. Garden Rhubarb or Pie-plant. — Lvs. smooth, cordate- 

 ovate, obtuse; petioles channeled above, rounded at the edges. — Native of Asia, 

 cultivated in gardens for the sake of the juicy, acid petioles. These are taken 

 in a green .'^tate, in the spring of the year, and made into tarts and pies, whose 

 excellence is well known to every one. Stem stout and fleshy, 3 — 4f high, 

 hollow, with large, sheathing stipules at the joints. Leaves very large, 1— 2f 

 long, I as wide, on petioles of nearly the same length. Panicle terminal, at 

 first enclosed in a white, membranous bract which at length bursts, disclosing 

 innumerable greenish-white flowers. May. 



2. OXYRIA. R. Br. 



Gr. o^vs, acid ; in allusion to the qualities of its leaves. 



Cal. 4-sepaled,2 inner sepals largest ; achenium 3-sided, with a "broad, 

 mUnbranaceous margin ; sta. 2 — 6 ; styles 2, stigmas large, plumose. — 

 % Lrs. mosily radical., petiolate. Stem nearly leafless., paniculate-raceviose. 



O. RENiFORMrs. Hook. (Rumex digynus. Linn.) Mountain, Sorrel. 



Radical Ivs. renilbrm, on long petioles; nvtcr .•sepals oblong, half as long as 

 the inner, valvular .sepals ; stamens 2 ; slylcs 2. — Found on the summits of the 

 White Mts., in moist ravines, and N. to "the Arc. Sea. The plant is acid to the 

 taste, like Rumex aceto.sus. Stem 3 — \' in height. June. 



3. POLYGONUM. 



Gr. roXvf, many, yovu, knee ; that is, plants with many joints. 



Sepals 4 — 6, mostly 5, connected at base, colored or corona-like, 

 persistent ; sta. 5 — 9, mostly 8 ; sty. 2 — 3, mostly 3, short, filiform ; 

 ach. mostly triangular, usually covered by the persistent calyx. — 

 Herbaceous. Sts. jointed. Fls. in axillary and trnninal fascicles and 

 spikes or pajiiculat'' racemes. 



