374 POLYGONACEAE 
6. POLYGONUM L. 
Annual or perennial, often somewhat shrubby herbs, with terete, but usually ridged 
erect or prostrate stems. Leaves alternate : blades leathery or somewhat fleshy, sometimes 
with two lateral impressions, articulated to the ocreae. Ocreae lobed when young, at 
length lacerate, hyaline, never fringed. Inflorescence axillary, consisting of clusters bear- 
ing normally several flowers at each node throughout the plant or confined to the branches 
and branchlets. Calyx of 5-6 partially united sepals. Sepals mostly green with white or 
pink margins, 2 wholly interior, 2 wholly exterior and 1 with one edge exterior and one 
edge interior, the outer sometimes corrugated in age, but not winged. Stamens varying 
from 3 to 8, often 5 or 6, included: filaments, at least the inner ones, dilated. Styles 3, 
usually distinct, sometimes very short. Achenes 3-angled, included or slightly exserted, 
brown or black, granular or smooth and shining. Endosperm horny. Cotyledons incum- 
bent. The plants flower in the summer and fall, except in the extreme southern part of 
our range. KNoTWEED. DooRwEED. KNOTGRASS. 
Stems branched at the base, the branches prostrate. 
Achenes exserted, chestnut-colored : calyx 5-7 mm. broad : sepals petaloid. 1. P. maritimum. 
Achenes included, black or brown: calyx 2-3.5 mm. broad : sepals not petaloid. 
Leaf-blades mostly acute: achenes not pinched at the apex. 2. P. aviculare. 
Leaf-blades mostly obtuse: achenes pinched at the apex. 3. P. littorale. 
Stems erect or ascending, more or less diffusely branched above. 
Fruits erect on the short stout icels. 
Leaf-blades without lateral impressions parallel to the midrib. 
Styles manifest. 
Leaves persistent: achenes granular and dull. 4. P. erectum. 
Leaves fugacious: achenes smooth and shining. 5. P. camporum . 
Styles wanting or nearly so. 6. P. ramosissimum. 
Leaf-blades with lateral impressions. 7. P. tenue. 
Fruits drooping from the slender reflexed or deflexed pedicels. 8. P. Douglasii. 
1. Polygonum marítimum L. Perennial or sometimes annual, glaucous, somewhat 
fleshy. Stem branched from the base, the branches prostrate, 2-7 dm. long: leaf-blades 
ovate, oblong or linear-oblong, 0.5-3 cm. long, generally equalling or exceeding the inter- 
nodes of the stem and branches, obtuse, revolute, strongly nerved especially beneath, 
somewhat rugose above: ocreae 0.5-1.5 cm. long, at length lacerate, bright and silvery, 
becoming brown at the base : clusters with 2 or 3 flowers : pedicels slender, 3-4 mm. long : 
calyx green about the base, 3 mm. long: sepals obovate, petaloid, rather obtuse, white or 
pink with a green rib: stamens 8: achenes 3.5-4 mm. long, ovoid, acute or acuminate, 
chestnut-colored, smooth and shining or minutely granular, conspicuously exserted. 
Along the coast, Maine to Florida and Alabama. Also in Europe. 
2. Polygonum aviculàre L. Annual or perennial, glabrous, dull green or bluish 
green. Stem usually branched from the base, the branches prostrate, 1-6 dm. Jong: leaf- 
blades oblong, linear-lanceolate or oblanceolate, 0.5-2 cm. long, usually acute or sometimes 
rather obtuse, not conspicuously nerved : ocreae 4 mm. long, silvery, becoming lacerate with 
age : clusters with from 2 to 5 flowers : pedicels slender, 1-2 mm. long : sepals oblong, obtuse, 
with white or pink borders: stamens 5-8: achenes 2.5 mm. long, ovoid, acute, dark 
brown, rounded at the base, rather pointed at the apex, granular and dull. 
Common throughout North America except the extreme north. Alsoin Europe and Asia. 
3. Polygonum littorale Link. Annual or perennial, bright green, often glaucous. 
Stem diffusely branched from the woody base, the branches prostrate, 3-12 dm. long ; inter- 
nodes often very short, especially at the ends or bases of branches ; the whole plant some- 
times dwarfed and reduced to a small, erect state less than 1 dm. tall: leaf-blades oblong, 
oblong-lanceolate or oblanceolate, 0.4-2 cm. long, usually obtuse or sometimes acutish, con- 
spicuously nerved, often crisped: ocreae 4-5 mm. long, silvery when young, at length 
lacerate and brownish : clusters often numerous, with from 2 to 6 flowers : calyx mostly green : 
sepals oblong, obtuse, with white borders, or sometimes red: stamens 8: achenes 2-2.5 
mm. long, broadly ovoid, usually somewhat constricted and often conspicuously so below 
the summit, enlarged and rounded at the base, dark brown, more or less granular, mostly 
dull, sometimes shining. 
moses dry soil, New Brunswick to British Columbia, North Carolina, Illinois and California. Also in 
4. Polygonum eréctum L. Annual, stout, green, or at length turning yellowish 
green. Stem erect, or ascending, with somewhat spreading branches, 2-6 dm. long: leaf- 
blades oval, oblong or obovate, 1-6 cm. long, obtuse or acutish : ocreae 0.3-1 cm. long, 
