17 P. convolvulus L. Knot-Bindweed. St. prostrate or climbing, twining, roughish; sheatlis naked; lvs. hastate, acuminate; fls. in axiilary fasicles or interrupted racemes; cal. obtusely keeled; ach. purplish-black, dull, exserted. - Fields and waste grounds, Can. to Car. Sts. angular, 2 to 3f long. Lvs. 1 to 2' by 7 to 15", petioles half as long. Cal. whitish, twice longer than the pedicels. Jl., Aug. § Eur.
18 P. cilinode Mx. Minutely pubescent, twining; sheaths girl at base with a ciliate hairy ring; lvs. deeply cordate, ovate, acuminate, lobes scarcely hastate; rac. paniculate, loose-flowered, axillary and terminal; ach. shining. - Fields and hedges, Can. to Wis. and Ga. St. slender, often reddish-purple, 3 to 6 to 8f long. Lvs. 1' to 18" by 9 to 15", petioles about half as long. Panicles simple, 5' long or less. Cal. wingless, scarcely keeled, not quite covering the brown achenium. Jl. - Sept.
19 P. dumetorura L. Hedge Eixdweed. St. smooth, twining and climbing; joints naked; lvs. cordate-hastate, acuminate, auricles acute; fls. in loose, pedunculate racemes which are naked or leafy; cal. with the 3 outer sep. acutely keeled and winged on the back, closely covering the smooth, black achenium. - Thickets, Can. and U. S. St. 3 to 8 to 12flong, climbing over bushes, etc. Lvs. 2 to 3' by 1 to 2', petioles nearly as long. Wings of the calyx narrower than the fruit, produced often at the apex. Jl. - Sept.
20 P. sagittatum L. Scratch Grass. St, prostrate, rough-angled; lvs. lanceolate-sagitate; fls. capitate; sta. 8; sty. 3. - Wet grounds, Can. and U. S. A rough, climbing species, 2 to 5f in length. St. square, the angles very rough with prickles pointing downwards. Lvs. acute, 2 to 3' long, a third as wide, with straight auricles and smooth stipules. Fls. in small, terminal heads, whitish. Jn.
21 P. arifolium L. St. aculeate with reversed prickles; lvs. hastate, acuminate, with divaricate, acuminate auricles; spikes few-flowered; fls. distinct; stam. 6; sty. 2. - Wet grounds, Can. to Ga. and W. States. Distinguished from the last by its larger, halbert-shaped leaves which are 2 to 4' long and 1/2 as wide. Petioles 1/2 to 1' long. Clusters racemous, slender, loose, few-flowered, at the ends of the branches. Jn., Jl.
8. FAGOPY'RUM, Tourn. Buckweat. (Gr. German
Eng. the beech, wheat; - beech-nut-wheat.) Calyx colored, equally 5-parted, spreading, withering, not enlarged in fruit; stamens 8, with 8 nectariferous glands between; styles 3; stigmas obtuse; ache-nia 3-angled, much exceeding the calyx. - Herbs with cordate-hastate lvs., oblique sheaths and panicled rac. of white-roseate fls.
F. esculentum Mœnch. Erect, smoothish; lvs. cordate with obtuse lobes; ach. angles wingless, entire, the sides ovate-triangular. - Old fields, sparingly naturalized, cultivated. St. 2 to 4f high. Lvs. 2 to 4' long, half as wide. Fls. numerous, very grateful to bees. Fruit black, a valuable grain, † § Asia.