BUCKWHEAT FAMILY 71 
Calyx mostly 5-parted, the divisions petal-like, erect and per- 
sistent. Stamens 3-9; styles 2-3-parted. Fruit lens-shaped 
or 3-angled.* 
1. P. aviculare L. KNore@rass. Annual or perennial. Stem pros- 
trate or ascending, diffuse, smooth, 6-24 in. long. Leaves small, 
lanceolate or linear-oblong, obtuse, nearly or quite sessile. Sheaths 
thin and dry, 2-3-cleft or cut. Flower clusters axillary, 1-5-flowered ; 
flowers inconspicuous, nearly sessile. Calyx greenish-white, 5-parted, 
the lobes with white or colored borders. Stamens 5-8; style 3-parted. 
Akene 3-angled. not shining. A common weed in dooryards and where 
the ground is trampled.* 
2. P. lapathifolium L. Annual. Stem branching, 1-4 ft. high. 
Leaves lanceolate or broader, wedge-shaped at the base and taper- 
ing from near the base to an extremely slender point, ciliate, vary- 
ing greatly in length. Sheaths not ciliate or fringed. Spikes oblong 
to linear, closely flowered, erect or nearly so, }-2 in. long. Calyx 
white or pink. Stamens 6: style 2-cleft. Akene ovate, lens-shaped, 
zy in. wide or less. In wet soil. 
3. P. acre HBK. Water SMarRTWEED. Perennial. Smooth or 
nearly so; stems erect or ascending, rooting below, 2-5 ft. high. 
Leaves lanceolate or broader, tapering at both ends, petioled, ciliate, 
translucent-dotted, acrid, 14-5 in. long. Sheaths cylindrical, falling 
early, bristly-fringed. Spikes erect or nearly so, loosely flowered, 3-3 
in. long. Calyx whitish-greenish or flesh color. Stamens 5; style 
usually 3-parted. Akene oblong, lens-shaped, smooth and shining. 
Swamps and wet soil, especially 3. 
4. P. PersicariaL. Lapy’s Tatms. Annual. Smooth or nearly so. 
Stem erect or ascending, 6-24 in. high. Leaves lanceolate or nar- 
rower, tapering at both ends, usually with a dark triangular or cres- 
cent-shaped spot near the center, very variable in length. Sheaths 
more or less bristle-fringed. Spikes ovoid or oblong, dense, erect, 
peduncled, 3-2 in. long. Calyx pink or purple. Stamens usually 6; 
styles 2-3-cleft more than half their length. Akene broadly ovate 
and lens-shaped, often somewhat triangular, smooth and shining. In 
waste ground, often a troublesome weed. Naturalized from Europe. 
5. P. hydropiperoides Michx. Mmp Water Pepper. Perennial. 
Stem smooth, slender, erect, decumbent, or prostrate, 1-3 ft. long. 
Leaves usually narrowly lanceolate, but variable. acute, ciliate, 2-6 
in. long. Sheaths wrinkled, bristle-fringed. Spikes erect, slender, 
often with the flowers scattered, }-2} in. long. Calyx pale pink, 
greenish or nearly white. Stamens 8: style 3-parted more than half 
its length. Akene 3-angled, smooth and shining. In swamps and 
wet places, especially S. 
