62 POLYGONACEAE 



Basal leaves long-petioled, oblong to lanceolate, acute at apex, cordate or subcordate at base, 

 3-20 cm. long; stem leaves linear to narrowly lanceolate, subsessile or clasping, often revolute 

 on the margins; raceme solitary, terminal, narrow, bearing reddish bulblets instead of flowers 

 toward the base ; calyx-lobes 5, pale rose or white ; stamens exserted ; achenes 3-angled, granu- 

 lar and dull. 



Meadows, Arctic and Hudsonian Zones; Alaska to Wallowa Mountains, Oregon, Colorado, Labrador and 

 New England'; also in Europe and Asia. Type locality: in Europe. June- Aug. 



24. Polygonum bistortoides Pursh. Western Bistort or Snakeweed. Fig. 1466. 



Polygonum bistortoides Pursh, Fl. Amer. Sept. 271. 1814. 

 Bistorta bistortoides Small, Bull. Torrey Club 33: 57. 1906. 



Perennial from a large fleshy horizontal chaffy rootstock, the stems erect, simple, 2.5-7 dm. 

 high. Basal leaves oblong to oblong-lanceolate or oblanceolate, 10-25 cm. long, acute or obtuse 

 at apex, acuminate at base, on petioles about as long as the blades, glabrous and more or less 

 glaucous; stem leaves sessile, mostly lanceolate, 3-15 cm. long, cordate or subcordate at base; 

 stipule-sheaths narrowly cylindric, oblique at apex; raceme solitary, terminal, densely flowered, 

 1-6 cm. long, 10-15 mm. broad; calyx-lobes 5, pale rose to white, about 4 mm. long; pedicels 

 3-7 mm. long, articulate at the base of the calyx; stamens exserted; achenes 3-angled, light 

 brown, smooth and shining. 



Mountain meadows and streams, Canadian and Hudsonian Zones; Arctic Alaska to southern California, 

 Colorado, and Arizona. Type locality: Weippe, Idaho, according to Piper, Contr. U.S. Nat. Herb. 11: 230. 

 1906. May-Aug. This is a variable species, and Greene (Pittonia 5: 197-200. 1903) proposed several segre- 

 gates, of which the following are in the Pacific States: P. ccphalophorum, P. vulcamcum, P. bernardmum, and 

 P. glastifolium. 



25. Polygonum phytolaccaefdlium Meisn. Alpine Knotweed. Fig. 1467. 



Polygonum phytolaccaefolium Meisn. ex Small, Mem. Dept. Bot. Columbia Univ. 1: 35. 1895. 

 Aconogonum phytolaccaefolium Small ex Rydb. Fl. Rocky Mts. 238, 1061. 1917. 



Stout perennial, 1-2 m. high, glabrous or sparsely pubescent, the stems more or less branched, 

 channeled. Leaves broadly lanceolate, 3-15 cm. long, 1-4 cm. broad, acute to acuminate at apex, 

 narrowed at base, coriaceous, short-petioled ; panicles ample, leafless or nearly leafless, loosely 

 flowered ; pedicels slender, 3 mm. long ; calyx-lobes white or greenish white, 3 mm. long, oboyate 

 to oblong; styles 0.5 mm. long; achene 3-angled, 4 mm. long, ovoid, acute, smooth and shining. 



Subalpine springs and moist slopes, Canadian Zone; Alaska to central California, east to Blue Mountains, 

 Oregon, Idaho, and Nevada. Type locality: California. This has been referred by some American authors to 

 the Old World species Polygonum alpinum Allioni or P. polymorphum Ledeb. June-Aug. 



26. Polygonum Newberryi Small. Newberry's Knotweed. Fig. 1468. 



Polygonum Newberryi Small, Bull. Torrey Club 21: 170. 1894. 



Perennial, the stems simple, usually several from a woody rootstock, decumbent or erect, 

 stout, 10-30 cm. high, often zigzag above, soft-pilose, usually reddish. Leaves mostly broadly 

 ovate, 1 . 5—^4 cm. long, obtuse at apex, usually cordate or subcordate at base, pallid, more or less 

 densely soft-pilose, at least the lower short-petioled; racemes short, few-flowered; calyx-lobes 

 greenish tinged with rose, 5, 2.5-3 mm. long ;_ stamens 8, included; style 3-parted ; achene 3- 

 angled, obovoid, light brown, smooth and shining. 



Rocky slopes, especially pumice, Boreal Zones; Cascade and Olympic Mountains, Washington, south to the 

 Lava Beds, Modoc County, California. A form with oblong-ovate, glabrous or subglabrous leaves occurs in the 

 vicinity of Mount Stuart, Washington. Type locality: near Crater Lake, Oregon. July-Aug. 



Polygonum Newberryi var. glabrum G. N. Jones, Rhodora 40: 359. 1938. Plants glabrous throughout, 

 otherwise like the typical species. Olympic and Wenatchee Mountains, Washington. 



27. Polygonum Davisiae Brewer. Davis' Knotweed. Fig. 1469. 



Polygonum Davisiae Brewer ex A. Gray, Proc. Amer. Acad. 8: 399. 1872. 



Stems several from a stout woody root, decumbent or erect, _somewhat fleshy, 1-4 dm. long, 

 simple or with a few short branches. Leaves ovate-oblong, 10-45 mm. long, acute or acutish at 

 apex, acute or obtuse at base, usually sessile or subsessile, scabrous-pubescent, with stout up- 

 wardly appressed hairs, sometimes very sparsely so ; flowers in short usually 3-4-flowered ra- 

 cemes; calyx-lobes greenish white, 3 mm. long; stamens 8; style 1 mm. long, 3-parted; achene 

 3-angled, 4 mm. long, exserted, usually narrowly ovoid. 



Alpine and subalpine, gravelly situations, Boreal Zones; Siskiyou Mountains, southern Oregon, to the 

 central Sierra Nevada, California. Type locality: Sierra Nevada, California. June-Sept. 



28. Polygonum natans (Michx.) Eaton. American Water Persicaria. Fig. 1470. 



Polygonum amphibium of Amer. authors, not L. 



Polygonum amphibium var. natans Michx. Fl. Bor. Amer. 1: 240. 1803. 



Polygonum natans Eaton, Man. ed. 3. 400. 1822. 



Polygonum Hartwrightii A. Gray, Proc. Amer. Acad. 8: 294. 1870. 



Persicaria oregana, P. purpurata, P. insignis, P. chelanica Greene, Leaflets Bot. Obs. 1: 27—49. 1904. 



Perennial, aquatic or rooting in mud, rarely branching above the base. Leaves usually float- 

 ing, 5-10 cm. long, ovate-oblong or elliptic, obtuse or acutish at apex, rounded or sometimes 

 subcordate at base, glabrous and shining above; peduncles glabrous; spike terminal, ovoid or 

 short-cylindric, 15-25 mm. long, densely flowered; calyx-lobes rose-colored, 4-5 mm. long; 



