§ 4. TOVÀRA. Perennials; flowers in loose naked long and slender spikes; calyx rather herbaceous (greenish), unequally 4-parted; stamens 5; styles 2, distinct, rigid and persistent on the smooth lenticular achene.
17. P. Virginiànum, L. Almost smooth; stem terete, upright (2–4° high); sheaths cylindrical, hairy and fringed; leaves ovate, or the upper ovate-lanceolate, taper-pointed, rounded at the base, short-petioled, rough-ciliate (3–6´ long); flowers 1–3 from each bract, somewhat curved, the styles deflexed in fruit, minutely hooked.—Thickets in rich soil, common. (Asia.)
§ 5. TINIÀRIA. Annuals or perennials, mostly twining or climbing, and with petioled cordate or sagittate leaves; flowers in loose panicles or racemes or in terminal or axillary clusters; calyx green with colored margins, 5- (rarely 4-) parted; stamens mostly 8; styles or stigmas 3 (2 in n. 18).
[*] Annuals, erect, or somewhat climbing by reflexed prickles on the angles of the stem and petioles; sepals (pale rose-color or white) not keeled; bracts chaff-like.
18. P. arifòlium, L. (Halberd-leaved Tear-thumb.) Stem grooved-angled; leaves halberd-shaped, taper-pointed, long-petioled; flowers somewhat racemed (few); peduncles glandular-bristly; calyx often 4-parted; stamens 6; styles 2, very short; achene lenticular (large).—Low grounds. (Asia.)
19. P. sagittàtum, L. (Arrow-leaved Tear-thumb.) Stem 4-angled; leaves arrow-shaped, short-petioled; flowers capitate; peduncles smooth; stamens mostly 8; styles 3, slender; achene sharply 3-angled.—Low grounds, common.—Slender, smooth except the angles of the stem and midrib beneath, which are armed with fine and very sharp saw-toothed prickles. (Asia.)
[*][*] Stems not prickly; calyx with the 3 outer divisions keeled, at least in fruit; flowers in loose panicled racemes; bracts short-sheathing.
P. convólvulus, L. (Black Bindweed.) Annual, twining or procumbent, low, roughish, the joints naked; leaves halberd-heart shaped, pointed; flowers in small interrupted corymbose racemes; outer calyx-lobes keeled; achene smoothish.—Cult. and waste grounds, common. (Nat. from Eu.)
20. P. cilinòde, Michx. Perennial, minutely downy; the sheaths fringed at the base with reflexed bristles; leaves heart-shaped and slightly halberd-shaped, taper-pointed; racemes panicled; calyx-lobes obscurely keeled; achene very smooth and shining.—Copses and rocky hills, N. Eng. to mountains of N. C., west to Mich, and Minn. Climbing 3–9° high.
21. P. dumetòrum, L., var scándens, Gray. (Climbing False Buckwheat.) Perennial, smooth; sheaths naked; leaves heart-shaped or slightly halberd-shaped, pointed; racemes interrupted, leafy; the 3 outer calyx-lobes strongly keeled and in fruit winged; achene smooth and shining.—Moist thickets, common. Twining 8–12° high over bushes.