406 PoLYGONACEAE 



13B. Stems 10-30 cm. long, not scandent 12. P. debile 



12B. Leaves ovate-deltoid or narrower, distinctly longer than viide. 



15A. Leaflike limb of stipules deeply toothed; midlobe of leaves narrow; achenes lustrous; stellate-pubescent. 



13. P. maackianum 

 1 5B. Leaflike limb of stipules entire or with a few deep incisions. 



16A. Petioles more or less winged; achenes dull, deep brown 14. P. thunbergii 



16B. Petioles not winged; achenes gray and lustrous 15. P. oreophilum 



IIB. Stipules without dilated limb. 



17A. Leaves gradually narrowed toward the petiole, entire; erect herb, the stems sparingly prickly 16. P. bungeanum 



17b. Leaves truncate to cordate, rarely rounded at base, often 3-lobed. 



18A. Stipules 3-4 mm. long, pilose; spikes 1- to 3-flowered 17. P. breviochreatum 



18B. Stipules 1-2 cm. long, glabrous or sparsely pilose, sometimes ciliate. 



19A. Inflorescence once or twice forked 1 8. P. hastatoauricuUtum 



19B. Inflorescence terminal and axillary, not forked. 



20A. Stipules obliquely truncate, scarcely ciliate, rather acute at the tip; leaves deeply cordate at base, glabrous or 



loosely ciliate on margin; pedicel shorter than the bract 19. P. sieboldii 



20B. Stipules nearly rectangularly truncate, ciliate; leaves truncate to shallowly cordate at base, setulose-scabrous on 

 margin. 

 21 A. Leaves with a rather distinct lobule on each side near base; pedicels longer than the bract. 



20. P. hastatosagittaUim 



21B. Leaves without distinct lobule on each side; pedicels shorter than the bract 21. P. nipponense 



lOB. Stems without prickles, glabrous or hairy. 

 22A. Stems not scandent; perianth-segments essentially unchanged in fruit. 



23 A. Annuals or rarely perennials; inflorescence a solitary spike or raceme, or compound; achenes small, lenticular or trigonous, 

 the pericarp coriaceous or crustaceous. 

 24A. Spikes globose or capitate. 



25A. Leaves with appressed sessile discoid glands beneath; stems to 30 cm. long 22. P. nepalense 



25B. Leaves without sessile discoid glands; stems longer 23. P. chinense 



24B. Spike cylindric to linear. 



26A. Stipules tubular, at least partly with a green dilated limb; leaves ovate or broadly so, cordate 24. P. orientah 



26B. Stipules without dilated limb. 



27A. Peduncles with stipitate glands 25. P. viscosum 



27B. Peduncles without stipitate glands. 

 28A. Stipules not ciliate. 



29A. Petioles adnate to the stipules nearly the whole length; aquatic or terrestrial perennial; spikes 1-2. 



26. P. amphibium 

 29B. Petioles adnate to the stipules near the base; annual terrestrial herbs without floating leaves; spikes few to 

 many. 

 30A. Stems 50-120 cm. long, stout, with thickened nodes; achenes small, about 2 mm. across; spikes to 10 cm. 



long, often nodding or pendulous 27. P. lapathifoUum 



30B. Stems to 60 cm. long, without thickened nodes; achenes 2-3 mm. across; spikes scarcely more than 5 cm. 



long, erect 28. P. scabrum 



28B. Stipules ciliate. 



31A. Perennials from long-creeping rhizomes; flowers rather large, loosely arranged, white or pink. 



32A. Flowers white; achenes lustrous 29. P. japonicum 



32B. Flowers pink; achenes dull 30. P. conspicuum 



3 IB. Annuals or biennials without rhizomes. 



33A. Perianth-segments distinctly glandular-dotted. 



34A. Achenes lenticular; leaves and other parts very acrid 31. P. hydropiper 



34B. Achenes trigonous; leaves not acrid 32. P. pubescens 



33B. Perianth-segments scarcely glandular-dotted. 



35A. Peduncles and upper internodes of stems and branchlets viscid 33. P. viscoferum 



35B. Peduncles and upper internodes not viscid. 



36A. Cilia of stipules 1-2 mm. long; spikes thick 34. P. persicaria 



36B. Cilia of stipules 3-10 mm. long; spikes rather slender. 



37A. Leaves ovate to lanceolate; ciliae of stipules elongate, usually as long as the stipules; plants of 

 woods, thickets and grassy places. 

 38A. Plant of woods, with vivid green leaves abruptly narrowed above, the tip often caudate; spikes 



loosely flowered, flowers pale rose-colored 35. P. caespitosum var. laxiflorum 



38B. Plant of sunny grassy places, thickets, or cultivated fields, with deep green leaves gradually nar- 

 rowed above, the tip obtuse; spikes densely flowered, pale-red, rarely white. . . 36. P. longisetum 

 37B. Leaves narrowly lanceolate to broadly linear, sometimes lanceolate; ciliae of stipules short or rather 

 elongate, usually shorter than the stipule; plants of wet grassy places along rivers. 

 39A. Leaves rather thick-membranous, often with indistinct discoid glands beneath. 

 40A. Achenes lenticular. 



41A. Spikes densely flowered, erect 37. P. kflwagoeanum 



41B. Spikes loosely flowered, often nodding 38. P. foUosum 



40B. Achenes trigonous 39. P. trigonocarpum 



