236 POLYGONACE^. 



Constituents. — Its only important constituent is a volatile oil. 



Preparations. — Oleum chenopodii — oil of chenopodium. — United States 

 Pharmacopoeia, The bruised seeds are sometimes administered in sub- 

 stance or decoction. 



Medical Properties and Uses. — Chenopodium is used solely as an an- 

 thelmintic for lumbricoid worms. 



POLYCO^ACE/E. 



Character of the Order. — Herbs with alternate, commonly entire leaves, 

 and stipules in the form of membranaceous sheaths above the swollen 

 joints of the stem. Flowers commonly perfect. Calyx 3- to 6-cleft, more 

 or less persistent. Stamens 4 to 12, inserted on the base of the calyx. 

 Ovary free, 1-ceiled ; styles or stigmas 2 or 3. Fruit a seed-like nutlet, 

 commonly triangular. 



An order comprising few North American genera, and these are largely 

 represented by common weeds, many of them possessing more or less 

 acrid properties. The most important plants of the order are buckwheat 

 {Fagopyruni) and rhubarb (Rheum). 



POLYGONUM. — Knotweed. 



Character of the Genus.— Calyx commonly 5-parted, the lobes often 

 petaloid, withering or persistent. Stamens 4 to 9. Styles or stigmas 2 or 

 3. Fruit a lenticular or triangular achenium, surrounded by the erect lobes 

 of the calyx. 



Polygonum Hydropiper Linne. — Smartweed, Water-Pepper. 



Description. — Flowers mostly greenish, in nodding S23ikes, usually short 

 or interrupted. Stamens 6. Style 2- to 3-parted. Achenium dull, minutely 

 striate, flat or obtusely triangular. A smooth annual, 1 to 2 feet high. 

 Leaves lanceolate, tapering to both ends, minutely pellucid-punctate. 



Habitat. — In damp places ; very common. 



Polygonum acre H. B. K. (P.punctatum Elliott). — Water Smartweed. 



Description, — Flowers whitish or flesh-colored, in erect spikes. Sta- 

 mens 8. Style mostly 3-parted. Achenium smooth, shining, sharply tri- 

 angular. A nearly smooth perennial. Stem ascending, rooting at the de- 

 cumbent base, 2 to 5 feet high. Leaves larger and longer than in the 

 preceding species. 



Habitat.— In wet places ; common, especially southward. 



Polygonum Bistorta Linne. —Bistort 



Description. — Flowers pink or white in a dense oblong or cylindrical 

 spike, 1 to 2 inches long, Styles 3. A perennial with a thick, cylindrical, 

 somewhat flattened rootstock. Stem erect, simple, 1 to 2 feet high, ter- 

 minating in a flower spike. Leaves mostly radical on long petioles, ovate- 



