158 POLYGONACEAE (BUCKWHEAT FAMILY) 



pointed, roughish, often marked with a dark triangular or lunar spot near the 

 middle : spikes ovoid or oblong, dense, erect, on smooth (or at least not glandu- 

 lar) peduncles-, stamens mostly 6: styles 2-3-cleft below the middle; achene 

 gibbous-flattened or sometimes triangular, smooth and shining. Naturalized 

 from Europe; not frequent in our range. 



10. Polygonum persicarioides H.B.K. Nov. Gen. 2: 197. 1817. Glabrous 

 or often strigulose, erect, decumbent or cre'eping; the stems 3-6 dm. long: 

 leaves from lanceolate to linear-lanceolate, acuminate at both ends, punctate, 

 petioled or sessile; sheaths conspicuously fringed with short bristles: inflores- 

 cence paniculate, somewhat compound: spikes erect, 2-6 cm. long, loosely 

 flowered : calyx rose-color, tinged with green : achenes narrowly ovoid or ob- 

 long, somewhat granular but shining. On our southeastern border to Mexico; 

 also in South America. 



11. Polygonum hydro piperoides Michx. Fl. Bor. Am. 1: 239. 1803. Peren- 

 nial, not acrid; stem smooth, 3-8 dm. high, branching: the narrow sheaths 

 hairy; leaves narrowly lanceolate, sometimes oblong: spikes erect, slender, 

 sometimes filiform, often interrupted at base, 2-5 cm. long: flowers small, 

 flesh-color or nearly white: sepals not dotted: stamens 8: achene sharply 

 triangular, smooth and shining. Wet places and in shallow water; across the 

 continent. 



12. Polygonum Hydropiper L. Sp. PL 361. 1753. Smooth, 3-6 dm. high, 

 juice very acrid: leaves punctate: spikes nodding, usually short or interrupted: 

 flowers mostly greenish: sepals conspicuously dotted: stamens 6: style 2-3- 

 parted; achene dull, strongly granular, either flat or obtusely triangular. 

 Ranging across the continent northward, where it is probably indigenous. 



13. Polygonum punctatum Ell. 1. c. 445. Annual, branching, 3-12 dm. 

 high, glabrous or the peduncles often minutely glandular: leaves lanceolate, 

 attenuate upward from near the cuneate base and acuminate, somewhat 

 scabrous with short appressed hairs on the midrib and margin, or rarely 

 floccose-tomentose beneath; sheaths and bracts rarely somewhat ciliolate: 

 spikes oblong to linear (1.5 to 5 cm. long), dense, erect or nearly so: flowers 

 white or pale rose-color: stamens 6: achene ovate, rarely 2 mm. broad. Wet 

 places; across the continent, mostly southward. 



14. Polygonum aviculare L. Sp. PI. 362. 1753. Slender, mostly prostrate 

 or ascending, bluish-green: leaves oblong to lanceolate, 6-20 mm. long, usually 

 acute: sepals scarcely 1 mm. long, green with pinkish margins: stamens 8 

 (rarely 5): achene dull and minutely granular, mostly included. (P. buxi- 



forme Small, Bull. Torr. Club 33: 56. 1906.) Variously called KNOTGRASS, 

 GOOSE GRASS, DOOR-WEED; introduced from Europe and growing everywhere 

 about yards and roadsides. 



15. Polygonum exsertum Small, Bull. Torr. Bot. Club 21: 172. 1894. An- 

 nual, slender, glabrous, erect, 3-8 dm. high, somewhat flexuous and ribbed: 

 leaves from obovate to narrowly lanceolate or linear: sheaths silvery or brown- 

 ish and much lacerate: flowers in small axillary clusters, greenish and incon- 

 spicuous: style 3-cleft or the stigmas often nearly sessile; achene triangular- 

 pyramidal, rounded at the base, much exserted from the calyx. From the 

 eastern part of our range to Maine. 



16. Polygonum erectum L. Sp. PI. 363. 1753. Stout, erect or ascending, 

 3-6 dm. high, yellowish: leaves oblong or oval, 1.5-6 mm. long, usually ob- 

 tuse: flowers mostly 3 mm. long, often yellowish, on more or less exserted 

 pedicels: stamens 5 or 6: achene dull, included. Texas and Colorado to the 

 Northwest Territory. 



17. Polygonum rampsissimum Michx. Fl. Bor. Am. 1: 237. 1803. Erect or 

 ascending, 6-12 dm. high, yellowish-green: leaves lanceolate to linear, 2.5-6 

 cm. long, acute, much reduced above: flowers and achenes as in the last, but 

 sepals more frequently 6, the stamens 3-6, and the achene mostly smooth and 

 shining. (P. rubescens Small, Bull. Torr. Bot. Club 33: 56. 1906.) Sandy 

 shores and banks of streams extending from Texas to the far north and west. 



18. Polygonum sawatchense Small, Bull. Torr. Bot. Club 20: 213. 1893. 

 Annual, somewhat scurfy: stem erect, 5-15 cm. high, usually somewhat 



