128 POLYGONACEAE. 



each bearing a linear-lanceolate tubercle on the back and 2 or 3 slender bristles 

 on the margins. 



Along the seashore, not common. This plant has generally been confused 

 with R. persicarioides L. 



Rumex obtusifolius L. Bitter Dock. Stems 40-60 cm. tall, erect; leaves 

 oblong-ovate, all cordate, 15-30 cm. long; flowers long-pedicelled, in loose 

 whorls; valves of the fruit ovate, fringed with a few bristly teeth, usually but 

 one valve tubercle-bearing. 



A troublesome weed, introduced from Europe. 



Rumex mexicanus Alcisn. Stems erect or decumbent, 40-90 cm. long, 

 slightly grooved, often branched below; leaves oblong-lanceolate or linear- 

 lanceolate, mostly acute, entire, rounded or cuneate at the base, 8-15 cm. long; 

 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. 



In wet places common., This species has been much confused with R. 

 salicifolius Weinm. 



Rumex crispus L. Yellozc Dock. Stem stout, 50-100 cm. high, grooved, 

 from an elongated fusiform root; leaves oblong, obtuse, truncate or rounded 

 at the base, 15-30 cm. long, the margin wavy and crisped; petiole short; 

 panicle rather dense, 20-40 cm. long, greenish; flowers on pedicels 5-10 mm. 

 long; valves 3-4 mm. long, broadly ovate or cordate, each bearing a tubercle; 

 akene about 2-2.5 mm. long, brown. 



An introduced European weed. 



Rumex conglomeratus Murr. Tall and slender; leaves ovate or lanceolate, 

 the lower cordate; panicle elongated, leafy; flowers in dense whorls, the pedicels 

 ver>' short; valves of the fruit all tubercle-bearing. 



A weed introduced from Europe. 



160. 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 or 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. P. convolvulus. 



Stems not twining; leaves not cordate. 



Leaves small, usually narrow; stems wir>\ 



Plant with woody rootstocks. P. paronychia. 



Plant without rootstocks; mostly annuals. 

 Plants prostrate. 



Akenes not longer than the calyx. P. aviculare. 



Akenes protruding from the calyx. P. fowleri. 



Plants erect or ascending. 



Flowers in rather dense terminal bracteate 



spikes; styles nearly obsolete. P. kelloggii. 



Flowers axillarj^ or in loose or interrupted 

 spikes; styles present. 



