604 ORDER 102. POLYGONACE^E. 



albuminous, with a straight or curved inverted embryo. Illust in Figs. 80, 375, 

 407, 408, 409, 413, 607, 103, 112. 

 Genera 33, species 690 (Meisner) widely diffused in all lands, but most abundant in the tem- 



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

 the root of Rheum palmatum and other species, native of fartary. But the leaves and utalks 

 of Sorrel, the petioles of Garden Rhubarb, etc., are agreeably tart, and contain oxalic acid ; the 

 petioles of the latter, together with the farinaceous seeds of the Buck-wheat, are well-known 

 articles of food. 



TRIBES AND GENERA. 



1. ERIOGONE^E. Flowers in dense, involucrate umbels, Ochreae EEIOGONUM. 1 



II. POLYGONE^E. Flowers not involucrate. Ochrese present (a) 



a Calyx 4-parted, regular. Stamens 6. Styles 2. Achenia winged OXYRIA. 2 



a Calyx 6-parted. Stamens 9. Sepals all similar, short RHEUM. :> 



a Calyx 6-parted. Stamens 6. Sepals 3, inner increasing, tuberculate RUAIEX. 4 



a Calyx 5-parted (irregularly 4-partcd in one species), (b) 



b Sepals, the 3 inner flmbriate-pectinate. Pedicels solitary TIIYSA.XELLA. 5 



b Sepals entire, 3, closed on the achenia, or all open. Pedicels solitary. POLYGONELLA. 6 

 all closed on the achenium. Pedicels usually fascicled.. POLYGONUM. 1 

 all open. Nectaries 8. Pedicels fascicled in the bract. . .FAGOPYIH'M. 8 



1. ERIOG'ONUM, MX. (Gr. ep^ov, wool, yovv, knee ; being woolly 

 at the joints, etc.) Flowers many in each common 5-toothed involucre ; ' 

 calyx deeply 5-cleft ; stamens 9 ; styles 3 ; achenia 3-angled or 3-lobed ; 

 embryo in or near the axis of scanty albumen. Herbs clothed with 

 dense cottony wool. Lvs. alternate, exstipulate, mostly at the base of 

 the stem, the upper bract-like, often whorled at the forks of the umbel- 

 late inflorescence. Invol. solitary or capitate. Pedicels within the in- 

 vol. 1 -flowered. 



1 B. tomentosum MX. Lower Ivs. crowded, spatulate, obovate or oblong, pe- 

 tiolate, beneath rusty white, tomentous, veins tawny red ; flowering branches 

 several times forked ; invol. solitary, campanulate, sessile, 5-toothed, loose-flow- 

 ered; cal. colored, funnel-form. U Sandy hills, S. Car. to Fla., frequent. St. 1 

 to 3f high. Lvs. 2 to 3' long, those of the stem much smaller. Fls. 3 to 4" long, 

 cream-white, with wool of the same color outside. Jn. Aug. 



2 E. longifolium Nutt. Lower Ivs. crowded, oblong-linear, with a long, attenu- 

 ated base, beneath white-tomentous, upper Ivs. scattered ; panicle ample, several 

 times forked ; bracts minu^ ; invol. solitary, campanulate, pedunculate many- 

 flowered ; cal. green, woolly. Fla. to Ark. St. 2 to 4f high. 



2. OXYR'IA, R. Br. MOUNTAIN SORREL. (Gr. o|vc, acid ; in allu- 

 sion to the qualities of its leaves.) Calyx herbaceous, 4-sepaled, the 2 

 inner sepals erect, larger, the 2 outer reflexed ; achenium lens-shaped, 

 thin, girt with a broad, membranous wing ; stamens 6, equal ; stigmas 



2, sessile, penicillate. 2 Low, nearly acaulescent, alpine plants. 



O. reniformis Hook. Radical Ivs. reniform, on long petioles ; outer sepals ob- 

 long, half as long as the inner, valvular sepals ; fruit orbicular. 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, nearly leafless, 

 racemed or subpaniculate. Jn. (Rumex digynus L.) 



3. RHE^UM, L. RHUBARB. (Rha, the river Volga, on whose banks 

 the plants are said to be native.) Calyx colored, 6-sepaled, persistent ; 

 stamens 9 ; styles 3, very short, spreading ; stigmas multifid, reflexed ; 

 achenia 3-angled, the angles margined. 2 Fls. fasciculate in racemous 

 panicles. 



R. Rhap6nticum L. GARDEN RHUBARB OB PIE-PLANT. Lva. ample, 

 smooth, cordate-ovate, obtuse ; petioles channeled above, rounded at the edges. 

 Gardens. Stem stout and fleshy, 3 4f high, hollow, with large, sheathing sti- 

 pules at the joints. Leaves very large, 1 2f long, f as wide, on petioles of 



