82 POLYGONACEAE (BUCKWHEAT FAMILY) 



EE. Mountain plant, in rocky soil; leaves not revolute; sheaths 4-6 mm. long; 

 flowers 2-3 together in the axils of the leaves. C. E. 



P. shastensis (SHASTA KNOTWEED) 



CC. Leaf blade longitudinally 3-veined, not jointed to the petiole. 

 F. Akene obovate; spike rather stout. 

 G. Sheath 6-8 mm. long, its segments rigid; upper leaves reduced. E. 



P. greenei 



GG. Sheath 2-3 mm. long, its segments not rigid; leaves much the same size 



throughout. E. p. parryi 



FF. Akene narrowly lanceolate; spike very slender; sheath about 2 mm. long; 



upper leaves reduced. W. C. P. californicum 



BB. Leaf blades not jointed to the petiole, at least some over i mm. wide; sheath 



not 2-lobed (except P. alpinum); flowers in most species in spikelike racemes; 



bracts small, scarious, or none. 



H. Perennial or annual, without rhizomes, mostly lowland plants; sheath cylindric, 

 truncate; stamens 4-8; akenes 3-angled or lens-shaped. 



I. Sheaths bristly-ciliate. 



J. Sepals dotted with dark glands; annual; akene lens-shaped or 3-angled. 

 K. Racemes drooping; akene granular or dull. W. E. 



P. hydropiper (WATER PEPPER) 

 KK. Racemes erect; akene smooth, shining. W. E. 



P. punctatum (DOTTED SMARTWEED) 

 JJ. Sepals not dark-dotted. 



L. Spike 3-6 cm. long, slender, not dense, interrupted; style 3-cleft; akene 



3-angled. W. E. P. hydropiperoides (MILD WATER PEPPER) 



LL. Spike 1.2-3.5 cm. long, thick, dense, not interrupted except sometimes at 



base; styles 2 or 2-cleft, rarely 3-cleft; akene lens-shaped, rarely 3-angled. 

 M. Leaves mostly with a dark blotch near the middle; plant glabrous, never 

 aquatic; spikes several. W. E. A bad weed in cultivated fields. 



P. persicaria (LADY'S THUMB) 



MM. Leaves not dark-blotched; plant hispid unless in water; spike only i. 

 W. E. P. hartwrightii 



II. Sheaths nearly or quite without cilia. 



N. Annual, in damp places; spikes several. 



O. Leaves white-tomentose beneath. E. P. tomentosum (WOOLLY SMARTWEED) 

 OO. Leaves not white-tomentose beneath. 



P. Spikes erect; akene orbicular. E. P. pennsylvanicum 



PP. Spikes drooping at least at tip; akene ovoid. 

 Q. Calyx and style each parted to below the middle. W. E. 



P. lapathifolium 



OQ. Calyx and style each parted nearly to the base. E. P. incarnatum 

 NN. Perennial, in water or mud; spike only i. 



R. Leaves oblong-elliptic, obtuse; spikes 1.2-2.5 cm- long; peduncles glabrous 



or nearly so. W. E. P. amphibium (WATER SMARTWEED) 



RR. Leaves ovate, acuminate; spikes 3-10 cm. long; peduncles hispid, often 



glandular. W. E. P. emersum (SWAMP SMARTWEED) 



HH. Perennial, with horizontal and elongated or cormlike rhizomes, alpine or 



subal pine plants; sheath oblique; stamens 8; akenes 3-angled. 

 S. Inflorescence of but i spikelike raceme, terminal; plants not growing in water 



nor particularly wet places. 

 T. Rhizome elongated; spike bearing flowers throughout. W. C. E. 



P. bistortoides 



TT. Rhizome cormlike; spike bearing bulblets at base. C. E. P. viviparum 

 SS. Inflorescence of more than i cluster, axillary and terminal; plants growing 

 in wet places. 



