BUCKWHEAT FAMILY 73 



Low plants; lower leaf-blades narrowed at the base; three tubercles. 



18. R. maritimus. 



8. OXYRIA Hill. Mountain Sorrel. i. O. digyna. 



9. POLYGONUM (Tourn.) L. Knotweed, Doorwbed, Knotgrass. 



Fruit erect. 



Inflorescence of small axillary clusters scattered more or less thoroughout the plant; 

 all except P. minimum with elongated stems or branches; perianth-lobes never 

 keeled near the apex. 

 Plants copiously leafy throughout; upper leaves scarcely reduced and more 

 crowded. 

 Very slender and low annuals, with red wiry, terete, non-striate stems. 



1. P. minimum. 

 Stouter and larger plants, often perennial, with prominently striate stems, 

 usually 3-8 dm. long. 

 Perianth-lobes with yellowish green margins; plant erect, with spreading 



branches in age; leaves broad, yellowish green. 2. P. erectum. 

 Perianth-lobes with white, pink or purplish margins; plant prostrate or 

 diffusely spreading; leaves from bright to pale bluisli green. 

 Leaves tliick, prominently veined, oblong, oval, or spatulate, obtuse or 

 roimded at the apex, usually pale; ocreae very conspicuous; 

 faces of the achenes granular. 3. P. buxiforme. 



Leaves tliin, not prominently veined, bright green; ocreae not conspicu- 

 ous; faces of the achenes finely striate. 

 Perianth 2.5-3.5 mm. long; achenes 2.5-3 mm. long, acute; leaves 



2-4 cm. long. 4. P. aviculare. 



Perianth 2-2.5 lum. long; achenes 2-2.5 mm. long, acuminate; leaves 

 mostly less than 2 cm. long. 5. P. negleclum. 



Plants with the upper leaves more scattered and reduced ; mostly erect perennials. 

 Upper bracts not subulate; achenes mostly dull. 



Lobes of the perianth with yellowish margins; perianth 3-4 mm. long; 



achenes about 3 mm. long, nearly smooth. 6. P. ramosissimum. 



Lobes of the perianth with whitish or pinkish margins; perianth 2-3 mm. 

 long; achenes 2-2.5 mm. long, distinctly granulate or striate. 

 Plant copiously branched and broom-like; leaf-blades Unear or nearly 



so ; achenes granulate. 7. P. proliflcum. 



Plant sparingly branched, mostly below; leaf-blades oblanceolate to 

 elliptic ; achenes finely striate. 8. P. rubescens. 



Upper bracts subulate; achenes smooth and sliining. 9. P. sawatchense. 



Inflorescence aggregate at the ends of the branches, or more scattered in P. parony- 

 chioides, in which, however, some of the perianth-lobes are keeled near the 

 apex ; bracts leaf-like and usually broader than the narrowly Unear leaves ; plants 

 dwarf annuals. 

 Perianth-lobes not keeled. 



Leaves several, gradually merging into the bracts; achenes blunt-angled and 



strongly striate. 10. P. Watsonii. 



Leaf usually solitary and much longer than the bracts; achenes sharp-angled 

 and obscurely striate. 11. P. uni folium. 



Some of the perianth-lobes keeled near the apex. 



Bracts herbaceous or the uppermost with a very narrow scarious margin. 

 Bracts linear; ocreae conspicuous; inflorescence interrupted. 



12. P. paronychioides. 

 Bracts oblong or narrowly oblong; ocreae inconspicuous; inflorescence con- 

 tiguous and dense. 13. P. Kelloggii. 

 Bracts with broad wliite petaloid margins. 14. P. polygaloides. 

 Fruit reflexed. 



Upper bracts much reduced and subulate. 



Perianth 1.5-2.5 mm. long; leaves narrowly linear. 15. P. Engelmannii. 



Perianth 3-5 mm. long. 



Outer perianth-lobes oblong, obtusish, tliickened and green or purplish on the 

 back; lower leaves oblanceolate to linear-oblanceolate. 



16. P. Douglasii. 

 Outer perianth-lobes obovate, rounded at the apex, merely with a narrow 

 midrib; lower leaves linear. 

 Inflorescence long, lax, virgate; ocreae of the bracts inconspicuous. 



' 17. P. majus. 

 Inflorescence dense, crowded at the ends of the branches; ocreae of the 

 bracts contiguous and conspicuous. 18. P. spergulariforme. 



Upper bracts foliaceous, relatively broad lanceolate or oblong. 

 Perianth 3.5-4 mm. long; lower leaves oblong or nearly so. 



Achenes included. 19. P. montanum. 



Achenes exserted. 20. P. commixtum. 



Perianth 2-2.5 mm. long; lower leaves obovate, very acute. 



21. P. Austinae. 



10. PERSICARIA (C. Bauhin) Mill. Smartweed, Lady's Thumb, Water 

 Pepper. 



Racemes terminal only and usually solitary; plants aquatic perennials. 

 Ocreae without spreading foliaceous tops. 



Plant usually floating, or decumbent and rooting ; leaves of an oblong type, glabrous, 

 acute or obtuse. 1. P. coccinea. 



