442 POLYGONACE^E. (BUCKWHEAT FAMILY.) 



15. P. acre, HBK. (WATER SMARTWEED.) Perennial, 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 3-parted ; achene smooth and shining. Wet 

 places ; common, especially southward. 



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

 and simple stems ; flowers 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 ; flowers 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. Virginianum, 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. TINlARIA. 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 8; styles or stigmas 3 (2 in n. 18). 



# Annuals, erect, or somewhat climbing by reflexed prickles on the angles of the 

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



18. P. arifdlium, L. (HALBERD-LEAVED TEAR-THUMB.) Stem grooved- 

 angle d ; 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 lenticular (large). Low grounds. (Asia.) 



19. P. sagittatum, L. (ARROW-LEAVED TEAR-THUMB.) Sterna-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 divisions keeled, at least in fruit , 



flowers 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; 

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

 achene smoothish. 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. Eug. to mountains of 

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



