POLYGONACEAE. 129 



Leaves rather broad, scarcely reduced 



upward. 

 Tall, branched throughout; style 



3-cleft. P. erectum. 



Low alpine plant ; style 3-parted. P. minimum. 

 Leaves narrow, decidedly reduced up- 

 ward. 

 Flowers in virgate much elongated 



loose spikes. P. douglasii. 



Flowers in interrupted but rather 



close spikes. 



Style 3-cleft ; filaments slender. P. spergulariaeforme. 

 Style 3-parted; filaments di- 

 lated. P. nuttallii. 

 Leaves comparatively large; flowers mainly terminal. 

 Annuals; flowers in several spike-like racemes. 



Ocreae naked; raceme drooping. P. lapathifolium. 



Ocreae bristly-ciliate. 



Calyx not glandular; raceme dense. P. persicaria. 



Calyx glandular; racemes interrupted. 



Racemes erect. P. punctatum. 



Racemes drooping. P. hydropiper. 



Perennials. 



Styles 3 ; plants with thick roots. 



Flowers in racemes or panicles; styles 



short. P. newberryi. 



Flowers in a single dense spike-like raceme; 



styles long. 

 Raceme thick not bulbiferous; akenes 



smooth. P. bistortoides. 



,. Raceme slender, often bulbiferous; 



akenes dull. P. viviparum. 



Styles 2; aquatic or swamp plants with flowers 



in spike-like racemes. 



Leaves ovate or lanceolate, acuminate. P. emersum. 

 Leaves oblong-elliptic, obtuse. 



Sheaths without foliaceous border. P. amphibium. 

 Sheaths with a spreading foliaceous 



border. P. hartwrightii. 



Polygonum convolvulus L. Annual; stems twining or prostrate, 50-100 

 cm. long, glabrous or pubescent, scurfy below; leaves heart-shaped or some- 

 what halberd-shaped, acuminate, 2-6 cm. long, minutely scurfy beneath; 

 petioles equalling or shorter than the blades; sheaths short; flowers in clusters 

 on slender axillary leafy racemes; calyx 5-parted, closely investing the fruit; 

 akene 3-angled, dull black, minutely roughened. 



Introduced in cultivated or waste soil. 



Polygonum paronychia Cham. & Schlecht. Perennial, half shrubby, 

 glabrous and somewhat glaucous; stems prostrate to ascending, irregularly 

 branched, 20-80 cm. long; leaves sessile, lanceolate, revolute on the margins, 

 strongly keeled beneath; sheaths silvery, lacerate, persistent on the old stems; 

 flowers in small clusters, axillary in the upper leaves and crowded near the 

 summit; calyx white or pinkish; stamens 8; akene 3-angled, black, smooth, 

 shiny. 



Along the ocean coast on sandy beaches. 



Polygonum aviculare L. Knot-weed. Annual, glabrous; stems slender, 

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