Polygonum. CX. POLYGONACEiE. 473 



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

 and yellow flowers. June — Sept. 



2 M nicHOTuMA. Mexican Fnur-o' clock. —Fls. sessile, erect, axillary, soli- 

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

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



3. M. LONGiFi-oRA. Lnn.'j,-p)vercd Four-o'clock.— Lrs. pubescent ; p. crowd- 

 ed ; tube of the cat. very long.— 71. Native of Mexico. Stem 2f high. Tube of 

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



Order CX. POLYGONACE^.— Buckwheats. 



Hfr6s,rarclys/jr«te, with alternate leaves. ,^ i'''^« °'lI.^^-'^'''""^*?*'"L*^rK'!'Pr£''[v?o 



Slip, of that remarkable kiiul called ochreffi, cohcniiR round the stem in the lorm of a sheath above the 

 Fls. mostly perfect, and in racemes. 

 Ca/.— riepals united at btise, imbricate in a-stivation. 

 Sta. definite, inserted on the ailyx near the base. 

 Ova. (tee. with a single erect ovulo. iityles or stigmas several. 

 !•>.— Achenium usually trianifuUir. 



Sds.— Embryo {reiiurally on one side of farinaceous albumen. 

 Genera 29, species 490, widely difl'used throughout the world. 



Provertie.^ —The roots of these plants are nau.seous and purgative. Rhubarb of the shops is the root 

 of .-onu. unknown species of this order, native .of Tai:tary, But the /mre* aiid staks «[«orrel, the gar- 

 den rhubarb, &c., are ajrreeably tart, and contain o.xalic acid ; the,pe loles of the latter, together with the 

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

 Co/ispcrMis of the Genera. 



U. Stigmas 3, multifid. 3 outer sepals smaller Rumex. 4 



(6. Stamens ^9. Stigmas muUitid. ••,.••,■., 5^f-"jr;„.« \ 



^mostly 5, united at l<a.-ie. persistent and enclosing the fruit Poljgrmum. Z 



Sepals ( 4. Radical leaves rcniform, on long petioles uxyna. ^ 



1. RHEUM. 



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



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

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

 fasciculale^ in racemose pajiides. 



R. Rhaponticum. Garden Rhubarb or Pie-plant. — I/vs. smooth, cordate- 

 ovate, obtu.se; 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 state, 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 enclo.sed in a white, membranous bract which at length bursts, disclosing 

 innumerable greenish-white flowers. May. 



2. OXYRIA. R. Br. 



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



Cal. 4-sepaled,2 inner sepals largest ; achenium 3-sided, with alDroad, 

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

 % Lvs. mostly radical^ pctiolate. Stem 7iearly lea/iess, paniculate-racemose. 

 O. RENiFORMis. Hook. (Rumcx digynus. Linn.) Mountain Sorrel. 

 Radical lvs. reniform, on long petioles ; oiiter sepals oblong, half as long as 

 the inner, valvular sepals ; stamens 2 ; styles 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 acetosus. Stem 3 — 4' in height. June. 



3. POLYGONUM. 



Gr. TToXvj, many, yo^'V, knee; that is, plants with many joints. 



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

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

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

 Herbaceous. St s. jointed. Fls. in a.villarij and terminal fascicles and 

 spikes or paniculate racemes. 



