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 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. 



BELDERDYKIA. 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. Pplygonum 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 

 revolute: 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.J 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, revqlute: 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), 



