POLYGONACEAE (BUCKWHEAT FAMILY) 157 



under Bistorta, 1. c. 20.] Subalpine and alpine in our range; arctic America, 

 Europe, and Asia. 



3. Polygonum amphibium L. Sp. PL 361. 1753. Aquatic, stout, gla- 

 brous or nearly so, not branching above the rooting base: leaves floating, 

 thick, smooth and shining above, usually long-petioled, elliptical to lanceo- 

 late, cuneate or cordate at base; sheaths leaf-bearing about the middle: spike 

 terminal, dense, ovate or oblong" 1-3 cm. long, on a" usually short peduncle: 

 flowers bright rose-color: the 5 stamens and 2-cleft style exserted. (P. plat- 

 tensis, P. subcoriacea, P. laetevirens, P. psychrophila, under Persicaria by 

 Greene, Leaflets 1: 29-31. 1904.) Colorado, north to the boundary, thence 

 across the continent. In shallow water or on muddy banks the stems become 

 erect, the petioles shorter, and the whole plant often more or less strigose- 

 pubescent. 



4. Polygonum emersum (Michx.) Brit. Trans. N. Y. Acad. Sci. 8: 73. 

 1889. In muddy or wet places, scabrous with short appressed or glandular 

 hairs, especially upon the leaves and upper part of the simple stem: leaves 

 thinner and longer, rather broadly lanceolate, acute or narrowly acuminate, 

 usually rounded or cordate at base: spikes more elongated, 5-7 cm. long, often 

 in pairs: flowers and fruit nearly as in the last. P. Muhleribergii. [P. Wardii 

 (Greene), under Persicaria, 1. c. 40.] 



5. Polygonum Hartwrightii Gray, Proc. Am. Acad. 8: 294. 1870. Closely 

 allied to the two preceding species, growing usually in the mud, the ascending 

 stems rooting at the base and very leafy, more or less rough, hairy, at least on 

 the sheaths and bracts: leaves rather narrow, on very short petioles, not 

 punctate, adnate to the middle of the sheath: flowers bright rose-color: sepals 

 not glandular-dotted: style 2-cleft, and achene somewhat flattened. (P. 

 muricidata Greene, under Persicaria 1. c. 47.) Transcontinental through the 

 northern States. 



6. Polygonum pennsylvanicum L. Sp. PI. 362. 1753. Stem 3-8 dm. high, 

 smooth below, the branches above and especially the peduncles beset with 

 bristly-stalked glands: leaves lanceolate, roughish on the midrib and margins: 

 spikes oblong, obtuse, erect, thick: flowers bright rose-color: stamens mostly 

 8, somewhat exserted: style 2-parted; achene lenticular. (P. omissum Greene, 

 Pitt. 5: 200. 1903.) Colorado and eastward to the Atlantic States. 



7. Polygonum lapathifolium L. 1. c. 360. Annual, branching, 3-12 dm. 

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

 attenuate upward from near the cuneate base and acuminate, s6mewhat 

 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. In 

 most parts of North America. 



7a. Polygonum lapathifolium incanum (Schmidt) Koch. Syn. Fl. Germ. 

 711. 1837. Lower, with shorter and less pointed leaves, which are lanceolate, 

 obtuse and white-downy beneath; sheaths often somewhat hairy or ciliolate: 

 spikes shorter, oblong and blunt. In the Wasatch, on the Saskatchewan, and 

 eastward to New York; rare. 



76. Polygonum lapathifolium nodosum (Pers.) Small, Monog. Polyg. 55. 

 1895. Generally robust and glabrous: stems red or reddish, marked with 

 purple spots and dark rings below the sheaths, much thickened at the nodes. 

 P. nodosum. Range about that of the species. 



8. Polygonum incarnatum Ell. Bot. S. C. & Ga. 1: 456. 1817. Stem 4-10 

 dm. high, nearly glabrous, the peduncles, etc., often minutely rough with 

 scattered sessile glands: leaves rough on the margins and midrib, elongated- 

 lanceolate: spikes linear, nodding, becoming slender: flowers smaller than in 

 the last, lighter rose-color shading to white: stamens 6 and styles 2, both in- 

 cluded: achene lenticular, biconcave, black, smooth and shining. Colorado 

 and Wyoming and eastward to the Atlantic States. 



9. Polygonum Persicaria L. Sp. PI. 361. 1753. Nearly smooth and gla- 

 brous, 3-5 dm. high: sheaths more or less bristly-ciliate ; leaves lanceolate, 



