APETALOUS EXOGENOUS PLANTS. 469 



EUPOLYGONELLA. Filaments all alike, subulate ; stigmas nearly sessile ; flowers 

 dioecious ly polygamous ; embj-yo in the center of ths albumen. 



P. GRACILIS, Mcisner. Annual; stem tall and slender, 

 paniculately branched above; leaves remote, Avedge-oblong, 

 obtuse, often wanting ; sheaths truncate, pointless; racemes 

 slender, scattered, forming a large and spreading panicle 

 on the sterile plant, more crowded on the fertile ; bracts 

 truncate ; floivers white or pale rose-color, the fertile ones 

 greenish; sepals all erect; valves oval or elliptical, unequal 

 (the interior longer), shorter than the ovate-lanceolate acu- 

 minate achenium. (Polygonum gracile, Nutt.) Dry sand- 

 ridges in the pine-barrens. September and October. Stem 

 2°-5° high ; leaves 1' long; racemes linear, 1-3' long. 



P. ARTicuLATA, Meisner. Annual ; stem much branched, 

 slender; leaves narrowly linear, obtuse, deciduous; sheaths 

 truncate, pointless; racemes numerous, erect, slender; 

 bracts truncate, open, the lowest ones pointed; flowers 

 bright rose-color; se2mls oval or roundish, nearly equal, 

 unchanged in fruit; interior filaments rhombic-ovate at the 

 base. Dry sandy soil. August. Stem 6-12' high; leaves 

 4:'-8' long ; racemes 1' long. 



POLYGONUM, L. Knotweed. 



Flotcers perfect ; calyx 5- (rarely 4) -parted, corolla-like, 

 the lobes nearly equal, erect and unchanged in fruit; sta- 

 mens 3-9 ; anthers roundish ; styles 2-3, distinct or partly 

 united; stigmas entire; achenium 3-angled or lenticular, 

 inclosed in the persistent calyx ; embryo curved on the out- 

 side of the albumen ; radicle slender. — Herbs, with alter- 

 nate, simple /eai^e^, and sheathing stipules', flowers com- 

 monly white or rose-color, variously disposed. 



Ambltgoxox. Flowers in cloi^ely-hr acted spikes ; stamens 7 ; style %-cleft / 

 achenium lenticular ; cotyledons incumbent ; albumen mealy. 



P. ORiENTALE, L. Hairy ; stem tall, branching ; leaves 



