Polygonum Polygonaceae 409 



Peduncles more or less pubescent and glandular; plants semiaquatic or 

 terrestrial; leaves ovate-oblong or ovate-lanceolate, very acute or 

 short-acuminate. 



Sheaths with herbaceous tips 8a. P. natans f . Hartwrightii. 



Sheaths without herbaceous tips 9. P. coccineum. 



Spikes several; annuals, preferring a rich, moist habitat. 



Peduncles copiously glandular-pubescent; spikes erect; stamens 8; achenes 

 2.2-3.5 mm wide. 

 Leaves copiously strigose-pubescent beneath and often above; achenes 



mostly 2.2-2.8 mm wide 10. P. pennsylvanicum var. genuinum. 



Leaves glabrous or glabrescent ; achenes mostly 2.5-3.5 mm wide. 



Glands of hairs red 10a. P. pennsylvanicum var. laevigatum. 



Glands of hairs without pigment 



10b. P. pennsylvanicum var. laevigatum f. pallescens. 



Peduncles without stalked glands, smooth or with sessile glands, rarely 



with a few stipitate glands; spikes drooping or erect; stamens 8; 



achenes 1.5-2.5 mm wide. 



Lower surface of leaves glabrous or scabrous on the principal veins; 



peduncles glabrous or rarely covered more or less with sessile 



glands; spikes 3-8 cm long, drooping; achenes generally less than 



2 mm wide 11. P. lapathifolium. 



Lower surface of leaves (at least the lower ones) scurfy or covered 



with a more or less deciduous, flocculent tomentum; peduncles with 



sessile glands; spikes 1-3 cm long, erect; achenes more than 2 



mm wide. (See excluded species no. 204, p. 1043.) . .P. tomentosum. 



Sheaths ciliate with a row of bristles. 



Stem and peduncles glandular-hispid 12. P. Careyi. 



Stem and peduncles not glandular-hispid. 

 Sepals glandular-dotted. 



Achenes dull, generally triangular; spikes usually strongly arched, the 

 flowers not far apart except toward the base of the spike, often 

 1 or more flowers in the axil of the next to the top leaf; flowers 

 greenish, generally with pinkish borders; stems often reddish, the 

 internodes short, generally 2-4 cm long; stamens 6. 

 Pedicels strongly exserted from the ocreolae; achenes 2-3 mm long. . . 



13. P. Hydropiper var. projectum. 



Pedicels not strongly exserted from the ocreolae; achenes mostly 



3-3.5 mm long. (See excluded species no. 200, p. 1042.) 



P. Hydropiper. 



Achenes shining, generally triangular; spikes elongated, flexuous, very 

 loosely flowered down to the first leaf but none below it; flowers 

 greenish, rarely purplish, with white borders; stamens 3-8; stems 

 with longer internodes than in the preceding, usually 3-8 cm 



L° n E 14. P. punctatum. 



Sepals not glandular-dotted or with only a few glands about the middle 

 of the perianth in forms of no. 16. 



Leaves lanceolate, 1-2.5 cm wide; spikes generally much less than 1 

 cm wide, erect or slightly flexuous; flowers 2-3 mm long. 

 Upper part of internodes of the stem mostly entirely glabrous; 

 spikes erect, mostly more than 7 mm wide, the longest usually 

 2-4 cm long; flowers generally close together; calyx lobes rose 

 color, usually slightly longer than the achenes; pedicels gen- 

 erally exserted less than 1 mm; stamens 6 



15. P. Persicaria. 



Upper part of internodes of the stem generally more or less strigose 

 below the node, usually for a third of its length; spikes gen- 

 erally more or less curved, mostly less than 7 mm wide, the 



