Calyx mostly 5-parted; the divisions often petal-like, all erect in fruit, withering or persistent. Stamens 4–9. Styles or stigmas 2 or 3; achene accordingly lenticular or 3-angular. Embryo placed in a groove on the outside of the albumen and curved half-way around it; the radicle and usually the cotyledons slender.—Pedicels jointed. Ours all herbaceous, with fibrous roots (except n. 19), flowering through late summer and early autumn. (Name composed of πολύς, many, and γόνυ, knee, from the numerous joints.)
§ 1. POLYGONUM proper. Flowers in axillary fascicles or spicate with foliaceous bracts; leaves and bracts jointed upon a very short petiole adnate to the short sheath of the 2-lobed or lacerate scarious stipules; stems striate; calyx 5–6-parted, usually more or less herbaceous; stamens 3–8, the 3 inner filaments broad at base; styles 3; cotyledons incumbent; albumen horny; glabrous annuals, except n. 1. (§ Avicularia, Meisn.)
[*] Leafy throughout.
1. P. marítimum, L. Perennial, at length woody at base (or sometimes annual), prostrate, glaucous, the stout stems very shortly jointed; leaves thick, oval to linear-oblong (3–10´´ long), exceeding the nodes; stipules very conspicuous; sepals petaloid; stamens 8; achene smooth and shining, exserted.—Sea-coast from Mass. to Ga. (Eu.)
2. P. aviculàre, L. Slender, mostly prostrate or ascending, bluish-green; leaves oblong to lanceolate (3–10´´ long), usually acute or acutish; sepals hardly 1´´ long, green with pinkish margins; stamens 8 (rarely 5); achene dull and minutely granular, mostly included.—Common everywhere in yards, waste places, etc. (Eu., Asia.)
3. P. eréctum, L. Stouter, erect or ascending (1–2° high), yellowish; leaves oblong or oval (½–2½´ long), usually obtuse; flowers mostly 1½´´ long, often yellowish, on more or less exserted pedicels, stamens 5–6; achene dull, included (P. aviculare, var. erectum, Roth.)—Common, by waysides, etc.
[*][*] Leaves much reduced above and bract-like.
4. P. ramosíssimum, Michx. Erect or ascending (2–4° high), yellowish green; leaves lanceolate to linear (1–2½´ long), acute; flowers and achene as in n. 3, but sepals more frequently 6, the stamens 3–6, and the achene mostly smooth and shining—Sandy shores and banks of streams, E. Mass to N. Y., west to Minn., Ark., Tex., and far westward.
5. P. ténue, Michx. Stem angled, erect (½–1½° high), glabrous, or slightly scabrous at the nodes; leaves narrowly linear to lanceolate (1–2´ long), 3-nerved, acute at each end and often cuspidate, the margins somewhat scabrous and at length revolute; flowers often solitary, nearly sessile; stamens 8; achene included, dull black—Dry soil, N. Eng. to S. C., west to Minn., Mo., and Tex.
6. P. campòrum, Meisn. Stem terete, erect or ascending (2–3° high), glabrous; leaves deciduous, linear to oblong, usually short; pedicels slender, exserted from the scarious sheaths; stamens 8.—E. Kan. to Tex.