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 

 scarious wings. 



*** Stems erect or ascending. 



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

 simple, erect, 12 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 



