442 POLYGONACE^. (BUCKWHEAT FAMILY.) 



15. P. acre, HBK. (Water Smartweed.) Pere??n/a/, nearly smooth ; 

 stems rooting at the decumbent base, 2-5° high ; leaves larger and longer 

 than in the last, taper-pointed ; spikes erect ; flowers whitish, sometimes flesh- 

 color; stamens 8; style mostly ^-parted; achene smooth and shining. — Wet 

 places ; common, especially southward. 



§ 3. BIST6RTA. Glabrous alpine perennials, with thick creeping rootstocks 

 and simple stems ; floicers in a spike-like raceme ; calyx colored, deeply 5- 

 cleft; stamens 8; styles 3, long. 



16. P. viviparum, L. Smooth, dwarf (4-8' high), bearing a linear 

 erect spike of flesh-colored flowers (or often little red bulblets in their place) ; 

 leaves lanceolate. — Alpine summits of N. Eng., shores of L. Superior, and 

 northward. (Eu.) 



§ 4, TOVARA. Perennials ; floicers in loose naked long and slender spikes; 

 calyx rather herbaceous {greenish), unequally 4-parted ; stamens 5; styles 2, 

 distinct, rigid and persistent on the smooth lenticular achene. 



17. P. Virginian um, L. Almost smooth ; stem terete, upright (2-4° 

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

 lanceolate, taper-pointed, rounded at the base, short-petioled, rougli-ciliate (3 - 

 6' long) ; flowers 1-3 from each bract, somewhat curved, the styles deflexed 

 in fruit, minutely hooked. — Thickets in rich soil, common. (Asia.) 



§ 5. TINIARIA. Annuals or perennials, mostly twining or climbing, and with 

 petioled cordate or sagittate leaves ; flowers in loose panicles or racemes or in 

 terminal or axillary clusters ; calyx green with colored margins, 5- [rarely 4-) 

 parted ; stamens mostly S; styles or stigmas 3 (2 in u. 18). 



* Annuals, erect, or somewhat climbing by reflexed jirirkles on the angles of the 

 stem and petioles ; sepals (pale rose<olor or ichite) not keeled ; bracts chafl'-like. 



18. P. arifolium, L. (Halberd-leaved Tear-thi-mb.) Stem grooved- 

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

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

 styles 2, very short; achene lenticular (large). — Low grounds. (Asia.) 



19. P. sagittatum, L. (Arrow-leaved Tear-thumb.) Stem ^-angled ; 

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

 mosth/ 8 ; styles 3, slender ; achene sharply 3-angled. — 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.) 



* * Stems not prickly ; calyx with the 3 outer divisions keeled, at least in fruit ; 



floicers in loose panicled racemes; bracts short-sheathing. 



P. Convolvulus, L. (Black Bindweed.) Annual, twining or procum- 

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

 floweis in small interrupted corymbose racemes; outer calyx-lohes keeled; 

 achene sniootliish. — Cult, and waste grounds, common. (Nat. from Eu.) 



20. P. cilinode, Michx. Perennial, minutely downy ; 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, N. Eng. to mountains of 

 N. C, west to Mich, and Minn. Climbing 3-9° high. 



