56 POLYGONACEAE 



1. Polygonum Paronychia Cham. & Sch. Beach Knotweed. Fig. 1443. 



Polygonum Paronychia Cham. & Sch. Linnaea 3: SI. 1828. 



Stems suffrutescent, much branched, prostrate or ascending, 2-10 dm. long, from a thick 

 woody rootstock, the older branches clothed with hyaline lacerated sheaths. Leaves usually 

 crowded, linear to oblong-lanceolate, 5-25 mm. long, articulate at the junction with the stipule- 

 sheath, strongly revolute, punctate and bright green on the upper surface, midrib on the lower 

 surface prominent with a 2-winged keel ciliate on the edges; flowers in the upper axils, crowded 

 at the ends of the branches ; calyx tinged with rose ; stamens 8 ; style 3-cleft to near the middle ; 

 achene 3-angled, 4.5-5 mm. long, black, smooth and shining. 



Sandy soils along the coast, Boreal and Humid Transition Zones; Vancouver Island, British Columbia, to 

 Monterey, California. Type locality: San Francisco, California. March-Sept. 



2. Polygonum shastense Brewer. Shasta Knotweed. Fig. 1444. 



Polygonum shastense Brewer ex A. Gray, Proc. Amer. Acad. 8: 400. 1872. 



Stems woody, prostrate or ascending, 1-3 dm. long, much branched from the stout woody 

 root. Leaves flat, but often becoming strongly revolute in age, oblong to oblong-oblanceolate, 

 acute or obtuse at apex, narrowed to the articulate base, 5-15 mm. long, glabrous on both sides, 

 the midrib not winged ; stipule-sheaths and bracts little or not at all lacerated ; flowers in axil- 

 lary clusters of 2 or 3 ; calyx rose-colored, with a dark midvein ; stamens 8 ; styles 3-parted to 

 the base ; achene 3-angled, 3 . 5-4 mm. long, oblong-ovoid, narrowed at both ends, chestnut brown, 

 smooth and shiny. 



Rocky or gravelly slopes, Hudsonian Zone; Cascade Mountains, Douglas County, Oregon, to the southern 

 Sierra Nevada, California, east to western Nevada. Type locality: Mount Shasta to Carson Pass, California. 

 July-Sept. 



3. Polygonum Fowled Robinson. Fowler's Knotweed. Fig. 1445. 



Polygonum Fowleri Robinson, Rhodora 4: 67. 1902. 

 Polygonum Rayi, American authors, not Babington. 



Herbaceous perennial, pale green or slightly glaucous, the stems prostrate, much branched, 



1-6 dm. long. Leaves pale green, elliptic to oblong-obovate, 6-25 mm. long, about equaling the 



internodes, obtuse at apex ; stipule-sheaths silvery, becoming lacerate ; flowers 2-4 in the axils ; 



calyx-lobes oblong, greenish, usually with white or roseate margins, achene ovoid, 3-angled, 



4-5 mm. long, well exceeding the calyx ; style 3-parted to the base. 



Seashores, Canadian and Humid Transition Zones; Alaska to the Puget Sound, Washington, also on the 

 Atlantic Coast from New Brunswick to Maine. Type locality: New Brunswick. July-Sept. 



4. Polygonum exsertum Small. Long-fruited Knotweed. Fig. 1446. 



Polygonum exsertum Small, Bull. Torrey Club 21 : 172. 1894. 



Erect branching annual, 4-8 dm. high, the stems slender, conspicuously striate. Leaves 1.5- 



3.5 cm. long, lanceolate to rarely oblanceolate, acute at apex, attenuate at base, subsessile; 



stipule-sheaths soon lacerate, silvery ; calyx-lobes 6, greenish with white margins ; stamens 5 or 



6; achene 3-angled, 5-8 mm. long, brown, smooth and shining, much exserted. 



Usually in sandy alkaline or brackish soils, Transition Zone; Blue Mountains, Washington, and Saskatche- 

 wan, to Nebraska, New Brunswick, and New Jersey. Type locality: not definitely stated. Aug.-Oct. 



5. Polygonum aviculare L. Common or Yard Knotweed. Fig. 1447. 



Polygonum aviculare L. Sp. PI. 362. 1753. 



Annual with pale or bluish green foliage, the stems slender, prostrate or ascending, simple 

 or often much branched, 1-12 dm. long. Leaves lanceolate to oblong-oblanceolate, 6-20 mm. long, 

 acute or acutish or sometimes obtuse ; stipule-sheaths silvery, becoming lacerate ; axillary clus- 

 ters 1-5-flowered ; calyx-lobes 5, scarcely 2 mm. long, green with pinkish or white margins ; 

 stamens 8, rarely 5 ; achene dull, minutely granular-striate, included or only the acute tip ex- 

 serted. 



A cosmopolitan weed, common in waste places, especially about yards and along paths. Native of Eurasia. 

 May-Nov. 



Polygonum aviculare var. angustissimum Meisn. in DC. Prod. 14: 98. 1857. (P. neglectum Besser.) 

 Leaves narrowly linear-lanceolate; achenes acuminate. About as widely distributed as the typical species. 



Polygonum aviculare var. littorale (Link.) Martens & Koch, Deutsche Fl. 3: 59. 1831. Prostrate or 

 sometimes dwarfed and erect, diffusely branched from the base, the internodes often very short. Leaves mostly 

 obtuse, thick; achenes somewhat shining, obscurely punctate. Along the coast of the Pacific States and in saline 

 soils of interior valleys, also Atlantic States and Europe. 



6. Polygonum argyrocoleon Steudel. Silver-sheathed or Persian Knotweed. 



Fig. 1448. 



Polygonum argyrocoleon Steudel ex Kunze, Linnaea 20: 17. 1847. 



Annual with pale green foliage, the stems erect with ascending branches, striate. Leaves 



linear, 1-3 cm. long, acute or acutish at apex, narrowed at base ; stipule-sheaths silvery above 



and becoming lacerate, the lower parts pale brown ; upper leaves reduced to inconspicuous bracts, 



the inflorescence appearing narrowly racemose or spicate ; flowers several in a cluster ; pedicels 



exserted ; calyx-lobes 6, green with roseate margins, 1 . 5 mm. long ; stamens 6 ; achenes 3-angled, 



ovoid, closely enveloped by the calyx-lobes, brown, smooth and shining. 



Recently introduced species, especially in alfalfa fields; Sacramento, San Joaquin, and Imperial Valleys, and 

 San Luis Obispo County. California, also southern Arizona. Native of Persia. June-Sept. 



