474 CX. POLYGONACE^E. POLYGONUM. 



1. AVICULARIA. Flowers axillary. Stamens 5 8. Stigmas 3. 



1. P. AVICULARE. Bird Polygonum or Knot-grass. 



St. procumbent ; Ivs. elliptical-lanceolate, rough-edged, acute, sessile ; 

 flowers subsessile. A common weed in fields, highways and door-yards, U. 

 S. and Brit. Am. Stems slender, \ l}f long, striate, smooth, branching, 

 with short, white, torn, remotely veined stipules at the joints. Leaves smooth 

 except the edges, 1' long and J as wide. Flowers reddish, small, 2 or 3 

 together in the axils of the leaves, appearing all summer. 



/?. glaucum. (P. glaucum. Nutt.} Lvs. fleshy, glaucous, revolute on the mar- 

 gin. Grows on the sea-coast, Long Island. 



2. P. ERECTUM. (P. aviculare. 0. latifolium. Michx.} Erect Knot-grass. 



St. mostly erect, branched ; Ivs. smooth, broadly oval, petiolate ; fls. pedi- 

 cellate ; sta. mostly 5. 7|. Western and Mid. States and Brit. Am. A species 

 remarkably distinct in appearance from the last, in similar situations, but sel- 

 dom growing with it. Stem 1 2jf high, branched, smooth. Leaves 1 2' 

 long and about } as wide, rather obtuse, the petioles f long. Flowers 23 

 together, pedicellate, in the axils of the leaves, yellowish. Jn. Sept. 



3. P. TENUE. Michx. (P. linifolium. MM.} Slender Knot-grass. 



St. slender, erect, branched, acute-angled ; Ivs. linear-lanceolate, erect, 

 acuminate ; slip, tubular, villose at top ; fls. alternate, subsolitary, axillary. 

 A small, slender plant, on rocky soils, N. Eng., Mid. States. Stem If high. 

 Leaves 1 1%' long, 1 2" wide, 3-veined, sessile. Flowers white. JL, Aug. 



2. PERSICARIA. Spikes terminal or axillary. 



4. P. PUNCTATUM. Ell. (P. Hydropiper. Michx. not of Linn.} Water 

 Pepper. St. branched, often decumbent at base ; Ivs. lanceolate, punctate 



with pellucid dots, waved and scabrous on the margin ; spike loose, interrupted, 

 drooping; sta. 6 8; sty. 2, united half way up. Q Can. to Flor. A plant 

 well known for its acrid taste, growing in ditches, low grounds, among rub- 

 bish, &c. Stem smooth, 'swelling above the joints, 2f high, and, like the 

 leaves, sprinkled with glandular dots, in which the acrimony is said to reside. 

 Leaves 2 3' long and not more than \ as wide. Flowers green, tinged with 

 purple and white. Aug., Sept. 



5. P. MITE. Pers. (P. hydropiperoides. Michx. P. barbatum. Walt.} 

 Mild or Tasteless Knot-grass. St. mostly decumbent at base, erect and 



hairy above ; Ivs. narrow, lanceolate, subhirsute ; stip. hirsute, long-ciliate ; 

 spikes linear ; bracts ciliate, subimbricate ; sta. 8 ; sty. 3. Ditches and ponds, 

 Can. to Car. and Tenn. Stem a foot or more high. Leaves 2 4' long, -| as wide, 

 sessile. Spikes several, crowded near the summit of the stem, composed of small 

 fascicles of reddish flowers. JL, Aug. See also Addenda, p. 638. 



G. P. PENNSYLVANICUM. Pennsylvanian Knot-grass. 



St. smooth, tumid at the joints; Ivs. lanceolate, petiolate; stip. glabrous, 

 not ciliate ; spikes oblong, crowded ; ped. hispid ; sta. 8; sty. 2 or 1. (J) Mar- 



nof ponds and ditches, N. H. to Car. Stem geniculate, branched above, 

 f high. Leaves 3 5' long, as wide, slightly scabrous. Spikes short and 

 dense, large, and somewhat nodding. Flowers large, rose-colored, pedicellate. JL 



7. P. LAPATHIFOLIUM. (P. incarnatum. Ell.} 



St. geniculate, smooth ; Ivs. ovate-lanceolate, petiolate, often hoary 

 beneath; spikes numerous, rather crowded, erect, on scabrous peduncles; sta. 

 6 ; sty. 2. A rare species in swamps and ditches, N. Y. to Ga. Stem 2 4f 

 high. Leaves 3 5' long, as wide. Petioles i \' long. Flowers small, 

 white, or tinged with red, in numerous, panicled spikes. Aug. 



8. P. PERSICARIA. Ladies' Thumb. Spotted Knot-weed. 



St. erect; Ivs. lanceolate, the upper surface spotted; stip. fringed ;. spikes 

 dense, oblong, erect; ped.- smooth ; sta. 6; sty. 2, half united. (J) A common 

 species about buildings, fences, wet grounds, &c. Stem smooth, branched, 

 leafy, 1 2f high, often colored. Leaves 2 4' long, i as wide, entire, short- 

 stalked, acuminate, generally marked with a brownish, heart-shaped spot near 

 the middle. Flowers rose-colored, in short, dense, terminal spikes. Jn.. Aug. 



