362 POLYGONACEAE (BUCKWHEAT FAMILY) 



roughish, often marked with a dark triangular or lunar spot near the middle ; 

 spikes ovoid or short-cylindric. dense, erect, on smooth (or at least not glandular) 

 peduncles ; stamens mostly 6 ; styles half 2-3-cleft ; achene gibbous-flattened or 

 sometimes triangular, smooth and shining. Waste and damp places, very 

 common. (Nat. from Eu.) 



23. P. setaceum Baldw. Perennial, stout, erect from a decumbent and 

 somewhat repent base, oppressed-hirsute ; sheaths fringed with very long coarse 

 bristles ; inflorescence and flowers as in the next, the achenes slightly larger, 

 black, shining. Mo. to S. C., Fla., and Tex. (Asia.) 



24. P. hydropiperoides Michx. (MILD WATER PEPPER.) Perennial, not 

 acrid; stem smooth (3-9 dm. high), branching; the narrow sheaths hairy; 

 leaves narrowly lanceolate, sometimes oblong ; spikes erect, slender, sometimes 

 tiliform, often interrupted at base (3-6 cm. long) ; flowers small, flesh-color or 

 nearly white ; sepals not dotted; stamens S; achene sharply triangular, smooth 

 and shining. (P. opelousanum Riddell.) Wet places and in shallow water, 

 centr. Me., westw. and southw. Var. STRIG^SUM Small (var. Macouni Small) 

 has the stem strigose, and is less frequent throughout our range. 



4. TOVARA (Adans.) Gray. Perennials; flowers in loose naked long and 

 slender spikes; calyx, rather herbaceous (greenish}, unequally 4-partedj 

 stamens 5 ; styles 2, distinct, rigid and persistent on the smooth lenticular 

 achene. 



25. P. virginianum L. Almost smooth ; stem terete, upright (6-12 dm. 

 high) ; sheaths cylindrical, hairy and fringed ; leaves ovate, or the upper ovate- 

 lanceolate, taper-pointed, rounded at the base, short-petioled, rough-ciliate 

 (7-15 cm. long) ; flowers 1-3 from each bract, somewhat curved, the styles 

 deflexed in fruit, minutely hooked. Thickets in rich soil, N. H. to Ont., Minn., 

 and southw. (Asia.) 



5. ECHINOCAtJLON Meisn. Erect or reclining annuals, armed with reflex 

 prickles on the angles of the stem, petioles, etc. ; flowers capitate or few in 

 a raceme ; leaves arrow- or halberd-shaped. 



26. P. arifblium L. (HALBERD-LEAVED TEAR-THUMB.) Stem grooved- 

 angled; leaves halberd-shaped, taper-pointed, long-petioled ; flowers somewhat 

 racemed (few); peduncles glandular-bristly; calyx often 4-parted ; stamens 6 ; 

 styles 2, very short ; achene lenticular (large). Low grounds, N. B. to Ont., s. 

 to Ga., O., and Mich. (Asia.) 



27. P. sagittatum L. (ARROW-LEAVED TEAR-THUMB.) Stem 4-angled; 

 leaves arrow-shaped, short-petioled; flowers capitate ; peduncles smooth ; stamens 

 mostly 8; styles 3, slender ; achene sharply 3-anyled. Low grounds, common. 

 Slender, smooth except the angles of the stem and midrib beneath, which are 

 armed with fine and very sharp saw-toothed prickles. (Asia.) 



6. TINlARIA Meisn. Twining (except dwarf var. of no. 29), unarmed; 

 leaves ovate-heart-shaped ; flowers in panicled racemes; outer calyx-lobes 

 keeled or winged. 



28. P. CONVOLVULUS L. (BLACK BINDWEED.) Annual, twining or procum- 

 bent, low, roughish, the joints naked ; leaves halberd-heart-shaped, pointed ; 

 flowers in small interrupted corymbose racemes ; outer calyx-lobes keeled or nar- 

 rowly winged ; achene minutely roughened, dull, black. Cultivated and waste 

 grounds, common. (Nat. from Eu.) 



29. P. cilin6de Michx. Perennial, minutely domiy ; the sheaths fringed at 

 the base with reflexed bristles ; leaves heart-shaped and slightly halberd-shaped, 

 taper-pointed ; racemes panicled ; calyx-lobes obscurely keeled ; achene very 

 smooth and shining. Copses and rocky hills, e. Que. to nits, of N. C., w. to 

 Minn, and Athabasca. Var. ERECTUM Peck (var. breve Peck) is a dwarf erect 

 form with the compound racemes chiefly terminal. 



30. P. scandens L. (CLIMBING FALSE BUCKWHEAT.) Perennial, smooth; 

 sheaths naked ; leaves heart-shaped or slightly halberd-shaped, pointed : 

 racemes interrupted, leafy ; the 3 outer calyx-lobes strongly keeled and in fruit 



