27 



17a. Leaves narrowly lanceolate or linear-oblong; rare species 



Knotweed, Polygonum ramosissimum. 



17b. Leaves broadly oblong, oval, or elliptical; common weed of 

 yards and gardens Knotweed, Polygonum erectum. 



18a. Leaves broadly triangular (3 7 dm. high; flowers white) 



Buckwheat, Fagopyrum esculentum. 

 18b. Leaves from linear to ovate or oblong 19. 



19a. Sepals 4; flowers in very long and slender spike-like racemes 

 (410 dm. high) Knotweed, Polygonum Yirglnianum. 



19b. Sepals 5; flowers in spikes or racemes 20. 



20a. Flowers on slender pedicels, forming a loose raceme; leaves 

 linear, jointed at the base (1 3 dm. high; flowers pink or 

 white; -chiefly near the Great Lakes) 



Jointweed, Polyg'onella articulata, 



20b. Flowers sessile or nearly so, forming a spike or spike- 

 like raceme 21. 



21a. Stipular sheaths at the base of the leaves ciliate at their upper 



margin 22. 

 21b. Stipular sheaths not ciliate at the upper margin 28. 



22a. Sheaths with spreading borders 23. 



22b. Sheaths without a spreading border, appre&sed to the 

 stem (Smartweed) 24. 



23a. Leaves ovate, acuminate; stem erect (1 2 m. high; flowers 

 pink) Prince's Feather, Polyg-onum orientale. 



23b. Leaves oblong, obtuse or subacute; spreading or ascending 

 plant of wet soil 



Water Smartweed, Polygonum amphibium yar. hartwrightii. 



24a. Peduncles with glandular hairs (5 15 dm. high) 



Smartweed, Polygonum careyi. 



24b. Peduncles not glandular (1 8 dm. high) (Smartweed) 25. 



25a. Sepals beset with minute black dots 26. 



25b. Sepals white, pink, or red, not black-dotted 27. 



26a. Racemes drooping or nodding at the tip; achene dull- 

 colored Smartweed, Polygonum hydropiper. 

 26b. Racemes erect; achene smooth and shining 



Smartweed, Polygonum acre. 



27a. Sheaths smooth; leaves usually with a dark 'spot near the base 



Smartweed, Polygonum persicaria. 

 27b. Sheaths hairy; leaves not dark-spotted 



Smartweed, Polygonum hydropiperoides. 



28a. Leaves obtuse or somewhat acute at the apex 29. 

 28b. Leaves acuminate at the apex (5 15 dm. high; flowers 

 white to pink) (Smartweed) 30. 



