158 pulygonaceab (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 gla;ndu- 

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

 gibbous-flattened or sometimes triangdlar, 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 creeping'; the stems 3-6 dm. long; 

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

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

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

 flowered: ealyx roSe-color, tinged with green: achenes narrowly ovoid or ob- 

 long, somewhat granular but shinihg.^^On'our southeastern border to Mexico; 

 also in South America. 



11. Polygonum hydropiperoides 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 

 triaingular, smooth and shining.-^- Wet places and in shallow water; across the 

 continent. 



12. Polygonuin Hydropiper L. Sp. PL 361. 1753. Smooth, 3-6 dm. hi^, 

 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 triangulai'. — 

 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: flcJWers 

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

 places; across the continent, mostly southward. 



14. Polygonvim aviculare L. Sp. PI. 362. 1753. Slender, mostly' prostratfe 

 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. btixi- 

 forme Small, Bull. Torr. Club 33: 56. 1906.)— Variously called Knotgbasb; 

 Goose Grass, Do(»ii-weed; introduced from Europe and growing everywhere 

 about yards and roadsides. 



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

 nual, slender, glabrous, erect, 3-8 dm. high, somewhat flexuous and ribhed! 

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

 ish and much lacerate: flowers in small axillary clusters, greenish and ineon' 

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

 pyramidal, rounded at the base, much exserted from the calyx.' — ^Frofn thfe 

 eastern part of our range to Maine. ' 



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

 3-6 dm. high, yellowish: leaves oblong or oval, 1.6-^ mm. long, usually obi 

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

 pedicels: stamens 5 or 6: achene dull, included.^ — ^Texas a:nd Colorado to the 

 Northwest Territory. 



17. Polygonum ramosissimum 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.)— Sahdy 

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



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

 .\nnual, somewhat scurfy: stem erect, 5-15 cm. high,' usually somewhat 



