POLYGONACEAE. 



85 



petioles rather short; panicle 10-12 cm. long, the branches short, leafy- 

 bracted; valves triangular-ovate, slightly toothed, 3-4 mm. long, each bearing 

 a large oblong tubercle; akene broad, 2 mm. long. Wet places, common. 



115. POLYGONUM. 



Annual or perennial, terrestrial or aquatic herbs, some species 

 woody; stems erect, prostrate, climbing or floating; leaves alter- 

 nate, sessile or petioled, continuous with or jointed to the cylindric 

 funnelform or 2-lobed often lacerate or fringed sheaths; flowers 

 small, perfect, green, white, pink or purple, variously clustered, 

 the clusters terminal or axillary; pedicels jointed, subtended by 

 the sheaths; calyx 4-5-parted or cleft, the outer segments larger 

 than the inner; stamens 3-9; stigmas capitate; akene lenticular 

 or 3-angled (rarely 4-angled), invested by or exceeding the calyx. 



Stems twining; leaves cordate. 



Stems not twining; leaves not cordate. 



Leaves small, jointed on the petioles; slender annuals. 

 Stems not striate; flowers in rather dense spikes with 

 imbricated bracts. 

 Bracts oblong, white-margined. 

 Bracts lanceolate, green. 

 Stems striate; flowers axillary or in loose or inter- 

 rupted spikes. 

 Branches not angled; leaves scarcely reduced 

 upwards. 

 Akenes exserted, smooth, shining; low alpine 



plant. 

 Akenes not exserted, dull; introduced usually 

 prostrate plant. 

 Branches angled; leaves decidedly reduced 

 upwards. 

 Flowers bell-shaped, 2-3 mm. long. 

 Flowers funnelform, 3.5-4.5 mm. long. 

 Leaves comparatively large, not jointed on the petioles. 

 Styles 3, long; flowers in a single dense spike-like 



raceme; root tuberous. 

 Styles 2-cleft; flowers in dense spikes; roots fibrous. 

 Perennial aquatic or swamp plants. 



Sheaths ciliate on the spreading border. 

 Sheaths not ciliate. 



Leaves elliptic, obtuse or acutish; pe- 

 duncles glabrous. 

 Leaves lance-ovate, acuminate; peduncles 

 hispid. 

 Annuals. 



Sheaths ciliate. 

 Sheaths not ciliate. 



Leaves not tomentose beneath. 

 Leaves tomentose beneath. 



P. convolvulus. 



P. polygaloides. 

 P. confertiflorum. 



P. 

 P. 



mminiunt, 

 aviculare, 



douglasii. 

 niajus. 



P. bistorloides. 



P. hartwrighlii. 



P. amphibium. 

 P. emersum. 

 P. persicaria. 



P. 

 P. 



lapathifolium. 

 tomentosum. 



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; 



