442 POLYGONACE^. (BUCKWHEAT EAMtLY.) 



15. P. acre, HBK. (Water Smartweed.) Pe?-ennm/, nearly smooth 

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

 than in the last, taper-pointed ; spikes ei'ect ; Jiowers ichitish, sometimes flesh- 

 color; stamens 8; style mostly 3-parted ; achene smooth and shining. — Wet 

 places ; common, especially southward. 



§ 3. BISTORTA. Glabrous alpine perennials, icith thick creeping rootstocks 

 and simple stems ; Jlowers in a spike-like raceme; calyx colored y deeply 5 

 cleft; stamens 8; styles 3, long, 



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

 erect spike of tlesh-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. TO VARA. Perennials ; Jlowers 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. Virginianura, L. Almost smooth ; stem terete, upright (2-4° 

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

 lanceolate, taper-pointed, rounded at the base, short-petioled, rough-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 ; Jlowers in loose panicles or racemes or in 

 terminal or axillary clusters ; calyx green ivith colored margins, 5- {rarely 4-) 

 parted ; stamens mostly 8; styles or stigmas 3 (2 in n. 18). 



* Annuals, erect, or somewhat climbing by rejlexed prickles on the angles of the 

 stem and petioles ; sepals {pale rose-color or white) not keeled ; bracts chaff-like. 



18. P. arifblium, L. (IIalberd-leaved Tear-thumb.) Stem grooved- 

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

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

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



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

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

 mostly 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 divisioiis keeled, at least in fruit , 



Jlowers in loose panicled racemes ; bracts short-sheathing. 



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

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

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

 achene smootliish. — Cult, and waste grounds, common. (Xat. 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 obscurelij keeled ; achene 

 very smooth and shining. — Copses and rocky hills, X. Eng. to mountains oi 

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



