370 BUCKWHEAT FAMILY. 



3. POLYGONUM, KNOTWEED, JOINTWEED. (Greek: many- 

 jointed.) Chiefly weeds ; some with rather showy flowers ; the follow- 

 ing are the commonest ; flowers late summer and autumn. 



§ 1. Flowers along the stem, nearly sessile in the axils of the almost 

 sessile linear or oblong leaves, small, greenish-white ; sheaths scarious, 

 usually cleft or torn and fringed. 



* Stems leafy throughout. 



P. marltimum, Linn. Glaucous, prostrate, the stems stout and short- 

 jointed ; leaves oval to linear-oblong, thick, surpassing the nodes ; stipules 

 very prominent. Seacoast, Mass., S. % ® 



P. aviculare, Linn. Common Knotweed or Doorweed. Generally 

 prostrate or creeping, bluish-green, growing everywhere in hard soils 

 , about yards, the stems and roots strong ; leaves small, oblong or lanceo- 

 late, acute or acutish ; sepals very small" green and pinkish. (J) 



P. ere'ctum, Linn. Erect or ascending, loose in habit, l°-2° ; leaves 

 oblong or oval and obtuse ; flowers larger than in the last, on more evi- 

 dent pedicels. Roadsides. ® 



* * Stems with much reduced or bract-like leaves above. 



P. ramosf ssimum, Michx. Nearly erect, much branched, and rigid 

 Striate stems 2°-4° high; lanceolate or linear leaves tapering into a 

 petiole, and a glossy akene ; sepals 6 and stamens 6 or 3, or else sepals 

 6 with 4 or 6 stamens. Mass., W. g) 



P. te'nue, Michx. Slender, upright, with thread-like branches, along 

 which the upper flowers form a loose leafy spike ; leaves narrow linear, 

 acute ; akene shining. Dry soil, N. Eng., S. and W. ® 



§ 2. Flowers collected in terminal spikes or spike-like racemes, rose-purple 

 or flesh-color, or rarely white or greenish. 



* ^Leaves lanceolate, oblong, or ovate, chiefly petioled ; sheaths cylindrical ; 

 flowers several from each bract of the spike, 6-parted. 



*- Sheaths and bracts not ciliate {except rarely in the first) nor fringed, 

 the sheaths without a border; sepals not punctate; style 2-cleft. 



** ® Spikes narrow or loose; leaves narrow. 



P. Iapathif61ium, Linn. Tall, l°-6° high ; leaves tapering from near 

 the base to a narrow point (4'-12' long); glabrous, or the peduncles 

 rough ■with scattered sessile glands ; spikes linear, nodding ; flowers 

 flesh-color or pale rose ; the 6 stamens and 2 styles included ; akene flat, 

 with concave sides. Wet places, N. Eng., W. "Very variable, one form 

 ' (var. incanum) with leaves hoary beneath. 



P. Pennsylvanicum, Linn. Stems l°-3° high, the branches above 

 and peduncles bristly with stalked glands ; spikes oblong, short and blunt, 

 erect ; flowers rose-purple ; stamens 8, a little protruding ; style 2-cleft ; 

 akene with flat sides. Common in moist places. 



++ ++ 2/ Spikes usually heavy and dense ; leaves broad. 



■ P. amphibium, Linn. Watek P. Chiefly N. ; in water, stems root- 

 ing below, often simple, bearing a single ovate or oblong dense spike or 

 head of pretty large and showy rose-red flowers ; leaves rather thick, 

 oblong, heart-oblong, lance-ovate or lanceolate, mostly long-petioled, 

 often floating ; stamens 6. 



P. Muhlenbe'rgii, Watson. Decumbent or nearly erect, rough with 

 short appressed or glandular hairs ; leaves thinnish, broad-lanceolate and 

 large, long-acuminate ; spike l'-S' long. Generally in muddy places, 

 N. Eng., W. and S. 



