314 SUMMER FLOWERS. 



thicker and more glaucous leaves, larger scarious stipules, 

 and larger flowers. 



P. amphibium : stems usually floating in water, rooting at 

 the lower nodes ; leaves oblong or lanceolate, spreading on the 

 surface; spikes terminal, solitary, supported on short pedun- 

 cles above the water, dense, cylindrical, rose-red. — Ponds and 

 watery ditches. Fl. June to September. On dry ground it 

 becomes a prostrate weed. 



** Stems twining. 



P. Convolvulus: annual; stems glabrous; stipules short; 

 leaves stalked, heart-shaped or broadly sagittate, pointed ; 

 flowers in little loose clusters, the lower axillary, the upper 

 forming loose irregular, terminal racemes. — Cultivated and 

 waste places. Fl. July to September. 



P. dumetorum is more luxuriant, and the three angles of 

 the fruiting perianth are more or less expanded into white 



*** Stems erect or ascending. 



P. Bistorta : leaves long-stalked, ovate, subcordate ; stems 

 simple, erect, 1-2 feet high, terminating in a dense, oblong, 

 or cylindrical spike of pretty pink flowers. — Bistort or Snake- 

 weed. — Moist pastures and meadows. Fl. June. 



P. Persicaria : annual; stems erect or spreading, branched, 

 glabrous, 1-2 feet high ; leaves lanceolate, often marked in 

 the centre with a dark spot ; stipules more or less fringed at the 

 top with short fine bristles ; spikes terminal, rather numerous, 

 oblong or cylindrical, dense, the flowers reddish, or sometimes 

 green. — Roadsides and waste places. Fl. June to September. 



P. lapathifolium, which closely resembles this, is distin- 

 guished by the pedicels and perianths being dotted with small 



