8. Polygonum Prolificum (Small) Robinson. Proliferous Knotweed

Fig. 1622

P.ramosissimum prolificum Small, Bull. Torr. Club 21:

171. 1894. P. prolificum Robinson, Rhodora 4: 68. 1902.

Annual, glabrous, stem erect or nearly so, 1 1/2° tall or less, usually much branched. Leaves narrow, spatulate, linear-spatulate or nearly oblong, rather slender-petioled, 5"-15" long, obtuse or acutish; ocreae inconspicuous, early much-lacerate; flowers exceeded by the ocreae; calyx sessile or nearly so, the sepals pinkish, slightly enlarged in fruit; stamens mostly 5; achene rhombic-ovoid, about 1 1/4" long, 3-angled, slightly roughened, abruptly contracted at the apex.

In brackish marshes and on the sea-shore, Quebec and Maine to Virginia; and in the interior from South Dakota to Missouri and Colorado. July-Oct.

9. Polygonum Atlanticum (Robinson) Bick-Nell. Atlantic Coast Knotweed

Fig. 1623

Polygonum ramosissimum atlanticum Robinson, Rhodora 4:

72. 1902. P. atlanticum Bicknell, Bull. Torr. Club 36: 450. 1909.

Annual, glabrous, bright-green, stem erect, 1°-3° tall, terete, but striate. Leaves narrowly elliptic or linear-elliptic, or broadest above or below the middle, slender-petioled, 10"-25" long, acute or slightly acuminate at both ends; ocreae brown, early much-lacerate; calyx long-pedicelled, the sepals 5 or rarely 6, with pink margins; stamens mostly 5; achene ovoid or rhombic-ovoid, about 1 1/2" long, 3-angled, smooth and shining.

In salt marshes and low brackish grounds, Maine to Rhode Island. Aug.-Sept.

Polygonum Bellardi All., admitted into our first edition, appears in our range only as a waif from the Old World.

10. Polygonum Erectum L. Erect Knotweed

Fig. 1624

Polygonum erectum L. Sp. Pl. 363. 1753.

Annual, glabrous, yellowish-green, stem erect or ascending, 8'-2° high, terete, nearly simple or much branched. Leaves oval, oblong or obovate, subses-sile or short-petioled, 3"-18" long, obtuse or subacute at the apex, conspicuously jointed to the ocreae; ocreae oblique, soon lacerate, silvery when young; flowers 1-2 together in the axils; sepals greenish-yellow or yellowish, enlarged in fruit; stamens 6 (sometimes 5); achene ovoid-pyramidal, 3-angled, 1"-1 1/2" long, dull, invested by the calyx, or the apex slightly protruding.

In moist or dry soil, Ontario to the Northwest Territory, Tennessee and Arkansas. July-Sept.

11. Polygonum Ramosissimum Michx. Mushy Knotweed

Fig. 1625

P. ramosissimum Michx. Fl. Bor. Am. 1: 237. 1803.

Annual, yellowish or yellowish-green, glabrous, stem erect or ascending, usually very much branched, slender, striate, usually rigid, 4'-4° tall. Leaves lanceolate or linear-oblong, short-petioled, 3"-2o" long, acute or acuminate at both ends; ocreae few-nerved, becoming deeply lacerate; flowers several together in the axillary clusters, short-pedicelled; sepals 5 or 6, yellow or yellowish, 1"-1 1/2" long; stamens 6 or fewer; achene 3-angled, acute, sometimes slightly protruding beyond the calyx, nearly 1 1/2"-2" long, black.

In saline soil, Minnesota to the Northwest Territory, New Mexico and California. July-Sept.

Polygonum camporum Meisn., admitted into our first edition, is here omitted as not certainly known within our area.