156 POLYGON ACE AE (BUCKWHEAT FAMILY) 



Spike usually solitary, short and thick. 



Sheaths neither spreading at summit nor fringed. 



Leaves obtuse or subacute . . . . . 3. P. amphibium. 



Leaves acute or acuminate . . . . . 4. P. emersum. 



Sheaths spreading at summit and somewhat fringed . 5. P. Hartwrightii. 



Spikes several or many, rarely few. 

 Sheaths cylindric, naked. 



Spikes erect; styles 2-parted; achene orbicular . . 6. P. pennsylvanicum. 

 Spikes drooping (at least at tip); style 2-parted; achene 



ovoid. 



Calyx and style each parted to below the middle . 7. P. lapathifolium. 

 Calyx and style each parted nearly to the base . 8. P. incarnatum. 



Sheaths cylindric, fringed with bristles. 

 Spikes erect. 



Achene lenticular or triangular; spike dense. 



Achene smooth, broadly ovoid . . . 9. P. Persicaria. 



Achene granular, narrowly ovoid .... 10. P. persicarioides. 

 Achene triangular; spike slender, open . . . 11. P. hydropiperoides. 



Spike drooping; achene lenticular or triangular. 

 Achene dull ai 



lull and granular ..... . 12. P. Hydropiper. 



. Achene smooth and shining ..... 13. P. punctatum. 



AVICULARIA. Mostly annuals, usually rather small, with nar- 

 row leaves; achene triangular 

 Plants prostrate-spreading ....... 14. P. aviculare. 



Plants erect. 



Flowers axillary throughout. 



Achenes conspicuously exserted . . 15. P. exsertum. 



Achenes included. 



Branched throughout, the branches spreading. 



Leaves from oblong to oval ..... 16. P. erectum. 



Leaves from oblong to linear 17. P. ramosissimum. 



Branched from the base. 

 Pedicels erect. 



Achene oblong ....... 18. P. sawatchense. 



Achene ovoid 19. P. tenue. 



Pedicels deflexed. 

 Achene ovoid. 



Upper bracts small and subulate . . . 20. P. Douglasii. 



Upper bracts foliaceous 21. P. montanum. 



Achene oblong ....... 22. P. Engelmannii. 



Flowers in terminal bracteate spicate-racemes. 

 Styles evident. 



Raceme long and interrupted 23. P. spergulariaeforme. 



Raceme very short, subcapitate. 



Bracts winged 24. P. polygaloides. 



Bracts not winged ....... 25. P. Watsonii. 



Styles wanting or nearly so 26. P. Kelloggii. 



BILDERDYKIA. Annual or perennial, the stem herbaceous 



and twining (Tiniaria). 



Outer calyx-segments unchanged in fruit .... 27. P. Convolvulus. 

 Outer calyx-segments developing wings . . . . 28. P. scandens. 



1. Polygonum bistortoides Pursh, Fl. Am. Sept. 271. 1814. Herbaceous 

 perennial with thick creeping chaffy rootstock; stem 2-6 dm. high: leaves few, 

 glabrous or with a minute hispid pubescence beneath; the radical on long 

 petioles, oblong, oblong-lanceolate to linear, either acute or obtusish at both 

 ends; the cauline much reduced and sessile upon the sheath, the margin often 

 re volute: flowers rose-color to white, on slender pedicels, in very dense ovate 

 to oblong spikes, and usually long-pedunculate: stamens and styles exserted: 

 achenes smooth and shining. [P. lilacina (Greene); P. calophylla (Greene), 

 both under Bistorta in Leaflets 1: 18 & 19. 1904.] New Mexico to Montana 

 and far northward and westward. 



la. Polygonum bistortoides linearifolium (Wats.) Small, Bull. Torr. Bot 

 Club 19: 252. 1892. Slender reduced alpine form with leaves tending to 

 linear: raceme ovoid. [P. linearifolia (Greene), under Bistorta, 1. c.] Alpine; 

 same range. 



2. Polygonum viviparum L. Sp. PI. 360. 1753. Perennial from a short 

 corm-like rootstock: stems 1-2 dm. high: leaves glabrous or rarely hispidulous 

 beneath; the radical oblong or lanceolate, 2-8 cm. long, varying from acute to 

 subcordate at base; cauline from narrowly lanceolate to linear, revolute: flow- 

 ers rather small, nearly sessile in linear spikes 2-5 cm. long, the lower flowers 

 at least replaced by sessile bulblets about 2 mm. long. [P. scopulina (Greene), 



