§ 2. PERSICÀRIA Flowers in dense spikes, with small scarious bracts; leaves not jointed on the petiole; sheaths cylindrical, truncate, entire, naked or ciliate-fringed or margined; calyx colored, 5-parted, appressed to the fruit; stamens 4–8, filaments filiform; cotyledons accumbent.
[*] Sheaths and bracts not ciliate or fringed; sepals not punctate; style 2-cleft.
7. P. lapathifòlium, L. Annual, branching, 1–4° high, glabrous or the peduncles often minutely glandular; leaves lanceolate, attenuate upward from near the cuneate base and acuminate somewhat scabious with short appressed hairs on the midrib and margin or rarely floccose-tomentose beneath; sheaths and bracts rarely somewhat ciliolate; spikes oblong to linear (½–2´ long), dense, erect or nearly so; flowers white or pale rose-color; stamens 6; achene ovate, rarely 1´´ broad. (P. nodosum, Pers., P. incarnatum, Man., in part.)—Wet places; N. Eng. and Can. to Ill., Wisc., and far westward. Very variable. (Eu.)
Var. incarnàtum, Watson. Leaves often large (6–12´ long, 1–3´ wide); spikes more slender and elongated (2–4´ long), nodding. (P. incarnatum, Ell.)—Penn. to Ill., Mo., and southward.
Var. incànum, Koch. Low (6–12´ high); leaves small, obtusish, more or less hoary beneath with floccose tomentum; spikes short.—Cayuga Lake, N. Y., Ont., shores of L. Superior, and northwestward. (Eu.)
8. P. Pennsylvánicum, L. A similar species, but the branches above and especially the peduncles beset with stipitate glands; flowers larger and often bright rose-color, in short erect spikes, often on exserted pedicels; stamens usually 8; achene nearly orbicular, over 1´´ broad.—Moist soil, in open waste places, common.
9. P. amphíbium, L. Perennial, aquatic or rooting in the mud, stout and glabrous or nearly so, not branching above the rooting base; leaves usually floating, thick, smooth and shining above, mostly long petioled, elliptical to oblong or sometimes lanceolate, acutish, cuneate or cordate at base (2–5´ long); spike terminal, dense, ovate or oblong (½–1´ long); flowers bright rose-color (1½–3´´ long); the 5 stamens and 2-cleft style exserted.—Widely distributed and rather common. (Eu., Asia)
10. P. Muhlenbérghii, Watson. Perennial, in muddy or dry places, decumbent or suberect, scabrous with short appressed or glandular hairs; leaves thinner, rather broadly lanceolate, narrowly acuminate (4–7´ long); spikes more elongated (1–3´ long), often in pairs; flowers and fruit nearly as in the last. (P. amphibium, var. terrestre, Gray, Manual; not Lurs)—N. Eng. to Fla., westward across the continent.
[*][*] Sheaths and bracts bristly ciliate or the sheaths foliaceously margined.
[+] Sepals not punctate; style 2-cleft; achene somewhat flattened.