360 POLYGONACEAE (BUCKWHEAT FAMILY) 



lanceolate. — Alpine summits of N. E., shores of L. Superior, Col., and Utah to 

 Alaska and Greenl. (Eurasia.) 



§ 3. PERSICAUIA [Tourn.] L. Flowers in dense spikes, with small scarious 

 bracts; leaves not jointed on the petiole ; sheaths cylindrical, truncate, entire, 

 naked or ciliate-fringed or margined ; calyx colored, b-parted, appressed to 

 the fruit; stamens -i-S ; filaments filiform ; cotyledons accumbent. 



Sheaths nearly or quite free from ciliation. 

 Annual ; achene compressed. 

 Faces of the achene umbonate ; style or stamens exserted • 17. P. longistylum. 



Faces of the achene concave ; stj'le and stamens included. 

 Achene '2.0—2.9 mm. broad. 



Leaves glabrous beneath 16. P. pennsylvanieum. 



Leaves more or less flocculent-tomentose beneath, or tardily 



glabrate . . . *. 12. P. tomentosum. 



Achene 1.5-2 mm. broad 11. P. lapathifolium. 



Perennial. 



Spikes several in pedunculate panicles 13. P. dejisiflorum. 



Spikes solitary or in pairs. 

 Leaves elliptical, obtuse or acute ; spikes 1.2-2A cm. long- ; pe- 

 duncles glabrous or nearly so 14. P. amphibium. 



Leaves lanceolate or ovate, acuminate ; spikes 3-10 era. Jong ; 



peduncles hispid, often glandular 15. P. Muhlenhergii. 



Sheaths bristly-ciliate. 



Stem and peduncles glandular-hispid . 18. P. Careyi. 



Stem and peduncles not glandular-hispid. 

 Sepals dotted with dark glands. 



Achene dull 19. P. Hydropiper. 



Achene shining 20. P. acre. 



Sepals not dark-dotted. 

 Annual. 

 Leaves ovate; sheaths often with an herbaceous border . 21. P. orientale. 



Leaves lanceolate ; sheaths without herbaceous border . , 22. P. Persicaria. 

 Perennial. 

 Sheaths with a spreading herbaceous border (14) P. amphihium, v. Ilariwrightii 



Sheaths without herbaceous border. 

 Appressed-bristly ......... 23. P. setaceum. 



Finely strigose or smoothi-jh 24. P. hydropiperoides. 



11. P. Iapathif51ium L. Annual, branching, 0,6-2.4 m. high, glabrous or 

 the peduncles obsoletely glandular; leaves lanceolate, attenuate upward from 

 near the cuneate base and acuminate, somewhat scabrous with short appressed 

 hairs on the midrib and margin ; sheaths and bracts rarely somewhat ciliolate ; 

 spikes slender (1-5 cm. long), somewhat panicled, den^e, erect or nodding; 

 flowers white or pale rose-color ; stamens (5 ; achene ovate, rarely 2 mm. broad. 

 (P. incarnatum of auth. and ? Ell., the latter merely a robust large-leaved form 

 with long drooping spikes.) — Wet places, common and variable. (Eu.) Var. 

 nod6sum (Pers.) Weinmann is a stout form with strongly nodose stems spotted 

 with red dots. 



12. P. tomentbsum Schrank. Annual, simple or moderately branched, 1-5 

 dm, high ; leaves lanceolate or lance-oblong, acute or barely acuminate, at least 

 the lower retaining more or less flocculent tomentum on the under suiface; 

 peduncles distinctly glandidar ; spikes thickish, the lateral scarcely peduncled; 

 flowers larger and mostly paler than in the last. — Moist ground, Nfd., e. Canada, 

 and N. E. to Cal. and B. C, (Eu.) Passes to the usually dwarf var. ixcAnum 

 (Schmidt) Giirke with leaves all permanently white-woolly underneath. (P. 

 lapathifolium, var. Koch.) — Sandy shores, sphagnum bogs and occasionally on 

 rubbish heaps, N. E, to N. J, and w^estw., chiefly along the Great Lakes. (Eu.) 



13. P, densifl5rum Meisn. Perennial, very stout ; leaves lanceolate, atten- 

 uate at each end, 2-3 dm. long, 3-6 cm. broad ; spikes several, slender, densely 

 flowered, rather rigidly erect, paniculate ; sheaths turbinate, much exceeded by 

 the slender pedicels ; styles 2 ; achene dark brown, strongly biconvex, smooth 

 and shining, 1.5 mm. broad. (P. portoricense Bertero.) — S. Mo, to S. C, La., 

 and Tex. (Trop. Am.) 



14. P. amphibium L. Perennial, aquatic or rooting in the mud, glabrous oi 

 nearly so, rarely branching above the rooting base ; leaves usually floating 

 smooth and shining above, mostly long-petioled, elliptical to oblong or some 



