132 POLYGONEiE, 



Ordee XXII. POLYGONE/E. 



Jussieu, Genera, 82 (1789). Pebsicari^, Adans. Fam. ii. 273 (1763). 



Herbs, or rarely shrubs, with alternate or whorled leaves of revolute 

 vernation ; stipules when present coherinj? around the stem and forming 

 a sheath. Inflorescence various, but commonly racemose and terminal. 

 Calyx of 4 — 9 nearly or quite distinct sepals, often colored and petaloid, 

 persistent. Stamens as many as the sepals, or fewer, perigynous. Styles 

 2 — 4, distinct or somewhat connate, opposite the angles of the len- 

 ticular or triquetrous 1-ovuled ovary. Fruit a compressed or trique- 

 trous achene. Seed erect ; embryo straight, in the midst of a fari- 

 naceous albumen, or ciirved around it. — An extensive family, containing 

 many homely and weedy plants ; but the tender leaves of the sorrels, 

 and petioles of rhubarb, abounding in oxalic acid, are valiied substitutes 

 for fruit in northern latitudes. The roots of the docks abound in tannin. 

 Buckwheat is a well-known cereal. There are the closest connections 

 between this order and the Caryophyllese on the one hand, and the 

 Amarantaceae on the other. 



Hints of the Genera. 



Leaves alternate, stipulate ; 



Sepals 4—6, equal, appressed to the achene, _-..-- i 



" " the oater smaller and spreading, ... - - 2 



Perianth tubular below, 6-lobed above, -------3 



" campanulate, 6-cleft, --------- 4 



Leaves alternate or verticillate, exstipulate ; 

 . Involucre wanting ; 



Flowers capitate, each with an herbaceous bract, - - 5 



Perianth tubular, cuspidately 6-toothed, - - - - 9 



Involucre tubular or campanulate, 



with 4 — 8 obtuse or merely acute teeth,^ . . - - . 6 



with 3—5 usually awned lobes, ----- - - 7 



with 3—6 cuspidate '>ften hooked teeth, - - - - 8 



Involucre 2-lobed, l-flowered, enlarged in fruit, ----- 10 



1, POLYGONUM, Columna. Herbs or undershrubs with alternate 

 entire leaves and sheathing stipules. Flowers small, in axillary fascicles 

 or terminal spikes or racemes. Perianth of 5 or 6 nearly distinct often 

 colored and petaloid sepals. Petals 0. Stamens 4-9, commonly in 2 

 sets or circles. Styles 2 or 3, distinct, or connate below, often very 

 short ; stigmas capitate. Fruit a triangular or lenticular achene, usually 

 closely invested by the persistent perianth. Embryo lateral, half 

 immersed in the hard albumen, curved : cotyledons narrow.— A vast 

 genus as now received by most botanists, but probably embracing several 

 quite natural genera. 



* Leaves jointed upon a short petiole adnate to the 2-lobed or lacerate sheath; 



flowers axillary to leaves or brads; filaments of the 3 inner stamens 



broad at base; achenes triquetrous; cotyledons incumbent. — 



Polygonum proper. 



•)- Glabrous and suffrulescent; sheaths conspicuous; sepals colored. 



