408 



POLYGONACEAE 



Polygonum 



^3o 

 Map 833 



Polygonum erectum L. 



stiffly ascending; leaves usually narrowly lanceolate or linear, mostly 1.5-5 

 cm long, usually acute or acuminate at both ends. 

 Sepal lobes with white or pinkish margins; normal achenes about 2.5 mm 

 long and included in the perianth (plants of autumn often have some 



or all of the achenes long-exserted) 1. P. exsertum. 



Sepal lobes with yellowish green margins; achenes 3-3.5 mm long (plants of 

 autumn rarely have exserted achenes). (See excluded species no. 202, 



p. 1043. ) P- ramosissimum. 



Plants not as above. 



Stems erect or ascending. 



Sepal lobes with yellowish green margins; stems generally solid and erect; 



leaves oval, elliptic, or obovate, generally acute 2. P. erectum. 



Sepal lobes with white or pinkish margins; stems generally hollow and 

 ascending; leaves like the preceding but smaller and usually nar- 

 rower 3. P. monspeliense. 



Stems prostrate, or diffusely spreading. 



Leaves thick, prominently veined, oblong, oval or spatulate, obtuse or 

 rounded at the apex, usually pale; ocreae very conspicuous; faces of 



the achenes granular 4. P. buxiforme. 



Leaves thin, not prominently veined, lanceolate or linear, acutish, acute, 

 or sometimes acuminate at the apex, light or dull bluish green; ocreae 

 not conspicuous; faces of the achenes finely striate. 

 Perianth 2.5-3.5 mm long; achenes 2.5-3 mm long, acute; leaves 2-4 



cm long, oblong-lanceolate, acute or obtusely pointed 



5. P. aviculare. 



Perianth 2-2.5 mm long; achenes 2-2.5 mm long, acuminate; leaves 

 mostly less than 2 cm long, linear-lanceolate or linear, acute (some- 

 times acuminate) at the apex 6. P. neglectum. 



Stems and branches strongly angled, erect; leaves linear, sharp-pointed, minutely 

 ciliolate 7. P. tenue. 



C. Flowers in terminal spikes. 



Styles short, soft, scarcely exserted, withering in fruit; leaves neither large- 

 ovate nor acuminate. 

 Sheaths not ciliate, except rarely the uppermost. 



Spikes 1 or 2, rarely 3; perennial, aquatic or marsh plants (sometimes 

 persisting for years or even spreading in a terrestrial form after drain- 

 age) with long rootstocks, rooting in the mud. 

 Peduncles glabrous; aquatic plants with floating leaves; leaves elliptic 

 or narrow-ovate, obtuse or subacute 8. P. natans. 



