144 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



45. POIYGONACEAE. Buckwheat Family. 



Sepals 6, the 3 outer ones unchanged in fruit, the 3 inner ones mostly developed into 

 wings 1. RUMEX. 



Sepals usually 4 or 5, those of the outer row often reflexed or enlarged at maturity, 

 Flowers axillary, solitary or clustered; leaf blades jointed at the base; stipule 



sheaths (ocrese) 2-lobed or laciniate 2. POLYGONUM. 



Flowers in terminal or axillary, spikelike, often panicled racemes; blades not 

 jointed; ocrese not lobed or laciniate. 

 Ocrese cylindric, truncate. 



Calyx curved; sepala4; stamens 4 3. TOVARA, 



Calyx not curved; sepals mostly 5, if fewer the stamens more than 5. 



4. PERSICARIA. 

 Ocrese oblique, more or less open toward the leaf. 

 Flowers with the outer sepals keeled or conspicuously winged at maturity. 



Plants twining vines; ocrese persistent 5. BILDERDYKIA, 



Plants very tall stout herbs, woody below; ocre;g fugacious. 



6. PLETIROPTERUS. 



Flowers with none of the sepals keeled or winged. 

 Stems ascending or reclining, armed with very numerous recurved prickles; 



ocrese persistent 7. TRACAULON. 



Stems erect, unarmed; ocrese fragile, soon withering 8. FAGOPYRUM. 



1. RTJMEX L. Dock. 



Plants small, with slender creeping propagating roots; foliage strongly acid; leaves 



hastately lobed 1. R. acetosella. 



Plants large; rootstocks stout, deep-seated; foliage slightly or not at all acid; leaves 

 not lobed. 

 Leaves flat, bright or pale green. 

 Pedicels several times as long as the wings; each of the 3 wings usually bearing a 



well-developed tubercle at maturity 2. R. verticillatus. 



Pedicels about equaling the wings; usually only one of the wings tuberculate. 



3. R. altissimus. 

 Leaves wavy or crisped at the margins, dark green. 



Wings with a few spreading bristle-like teeth 4. R. obtusifolius. 



Wings entire or nearly so. 

 Blades of lower leaves narrowed at base; usually only one of the wings tuber- 

 culate 5. R. patientia. 



Blades of lower leaves cordate or obtuse at base; all 3 of the wings usually 

 tuberculate 6. R. crispus. 



1. Rumex acetosella L. Sheep sorrel. 

 Dry fields and rocky hillsides; abundant. Summer. Nearly throughout N. Amer.; 



naturalized from Eur. 



2. Rumex verticillatus L. Swamp dock. 

 Swamps and moist alluvial situations; several localities, principally along the upper 



Potomac. May-July. Eastern N. Amer. 



3. Rumex altissimus Wood. 



Moist alluvial situations; not uncommon, especially along the Potomac. Apr.- 

 June. Eastern U. S. 



4. Rumex obtusifolius L. Bitter bock 

 Waste places; common. Summer. Nearly throughout N. Amer.; naturalized from 



Eur. 



