This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol1", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Annual or sometimes perennial prickle-armed herbs, with reclining-climbing 4-angled stems. Leaves alternate, truncate, hastate or cordate, membranous, the petiole, midrib and principal nerves armed with small recurved prickles. Ocreae oblique, finely nerved, variously roughened about the base. Flowers in terminal and axillary spike-like racemes, these usually somewhat interrupted, or in capitate clusters. Sepals somewhat colored, 4-5, neither keeled nor winged, enveloping the achene. Stamens varying from 5 to 8, included; filaments not dilated. Styles 2 or 3, partially united, included. Achenes lenticular or 3-angled, variously colored, strongly biconvex or three-angled, smooth and shining. Endosperm horny. Cotyledons accumbent. [Greek, rough-stem.]
About 18 species, natives mostly of North America and Asia. Type species: Tracaulon ari-folium Raf.
Leaves sagittate; achene 3-angled.
Leaves halberd-shaped; achene lenticular.
Polygonum sagittatum L. Sp. PI. 363. 1753-Tracaulon sagittatum Small, Fl. SE. U. S. 381. 1903.
Annual, light green, stem slender, weak, decumbent, or climbing over other plants by the abundant sharp recurved prickles which arm its 4 prominent angles. Leaves lanceolate-sagittate or oblong-sagittate, ¥-3 long, obtuse or acute at the apex, slightly rough on the margins, the lower petioled, the upper subsessile; petioles and lower surface of the midribs prickly; ocreae oblique, not ciliate, fringed at the base by a few bristle-like prickles; flowers in rather dense terminal heads or racemes; calyx greenish or rose-colored; stamens usually 8; style 3-parted to below the middle; achene 3-angled, oblong-pyramidal, thick-pointed, 1 1/2" long, dark red, smooth, shining.
In wet soil, Newfoundland and Nova Scotia to the Northwest Territory, south to Florida and Kansas. Ascends to 3000 ft. in Virginia. July-Sept.
Polygonum arifolium L. Sp. PI. 364. 1753. Tracaulon arifolium Raf. Fl. Tell. 3: 13. 1836.
Perennial, stem ridged, reclining, 2°-6° long, the ridges armed with recurved prickles. Peduncles and pedicels glandular or pubescent; leaves broadly hastate, long-petioled, i'-i0' long, pubescent or glabrous beneath, the apex and basal lobes acuminate; petioles and stronger nerves prickly; ocreae oblique, fringed at the summit with short bristles and at the base with slender prickles; flowers in terminal and axillary heads or racemes; calyx rose-color or greenish, 4-parted; stamens 6; style 2-parted; achene lenticular, broadly obovate, 2" long, strongly biconvex, dark brown, smooth, shining.
In moist or wet soil, New Brunswick and Ontario to Minnesota, south to Georgia. Sickle-grass. Scratch-grass. July-Sept.