586 THE POLYGONUM FAMILY. [Pdygonum. 



spike, 1 to 2 inches long. Perianth pink or rarely white. Styles 3. 

 Stamens longer than the perianth. 



In moist pastures, and meadows, chiefly in hilly districts, in Europe, 

 central and Russian Asia, and northern America, extending into the 

 Arctic regions. Occurs in various parts of Britain, chiefly in the north 

 of England and south of Scotland, but is local, and in some instances a 

 straggler from gardens. PL summer. 



7. P. amphibium, Linn. (fig. 875). Amphibious P. A glabrous 

 perennial, usually floating in water, and rooting at the lower nodes. 

 Leaves oblong or lanceolate, rather thick, 3 to 6 inches long, spreading 

 on the surface of the water. Spikes terminal, solitary or rarely 2 

 together, supported on short peduncles above the water, dense and 

 cylindrical, 1 to 1^ inches long, of a rose-red. Stamens usually 5. 

 Styles 2. Nuts flattened. 



In ponds and ditches, in Europe, central and Russian Asia, and 

 northern America, to the Arctic regions. Extends all over Britain. 

 Fl. gummer. When growing in dried-up ponds or muddy ditches the 

 stems are creeping at the base, then shortly erect, and the leaves are 

 often downy. 



8. P. Persicaria, Linn. (fig. 876). Pcrsicaria. An erect or spread- 

 ing, branched annual, glabrous or slightly hoary, and often turning red, 

 1 to 2 feet high. Leaves lanceolate, stalked, or the upper ones sessile ; 

 the larger ones 3 to 5 inches long, and an inch broad or rather more, 

 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, and seldom above an inch long, dense, 

 but not so regular as in P. amphibium, and there is often a cluster of 

 flowers a little below. Flowers reddish or sometimes green, not dotted. 

 Stamens usually 6. Styles usually 2. Nuts flattened but rather thick, 

 smooth and shining, and often concave on one side. Occasionally there 

 are 3 styles, and the nut is then triangular. 



In ditches, on roadsides, in cultivated and waste places, throughout 

 Europe and central and Russian Asia to the Arctic regions. Abundant 

 in Britain. Fl. all summer and autumn. It varies much in stature and 

 in colour, in the number and density of the spikes, and in the achenes 

 more or less concave or convex on one or both sides. 



9. P. lapathifolium, Linn. (fig. 877). Pale P. Closely resembles 

 P. Persicai"ia, and is probably a mere variety, distinguished by the 

 pedicels and perianths dotted with small prominent glands. The 

 colour of the plant is usually pale green, the stipules seldom fringed, 

 and the nuts usually concave on both sides, but these characters are not 

 constant. 



In cornfields and waste places, with nearly the same range as P. Per- 

 ticaria, but usually in richer soils, and does not extend so far north. In 

 Britain not uncommon. Fl. summer and autumn. Specimens agreeing 

 with P. Persicaria in everything but the glandular dots have been de- 

 scribed as a third species under the name of P. laxum or P. nodosum. 



10. P. Hydropiper, Linn. (fig. 878). Watcrpcpper P. Stature and 

 foliage nearly as in /'. Persicaria, but a more slender plant, often 

 decumbent or even creeping at the base, the stipules more fringed at 

 the top, the leaves narrower, and the flowers in slender spikes, often 2 

 or 3 inches long, more or less nodding, the clusters of flowers almost 



