POLYGONACEJ;. 715 



Root stock perennial. Spikes solitary or rarely two. 



Leaves oblong-linear. Spikes slender and linear . 5. Viviparous P. 

 Leaves ovate or oblong-lanceolate. Spike dense, ob- 

 long or cylindrical. 

 Styles 3. Leaves chiefly radical. Stem-leaves few 



and small 6. Bistort P. 



Styles 2. Stem floating or ascending, with large, 



oblong, stalked leaves 7. Amphibious P. 



Annuals. Stems branched with several spikes. 

 Spikes dense, seldom above an inch long. 



Pedicels and perianths quite smooth. Stipules 



usually fringed 8. Persicaria P. 



Pedicels and perianth rough with glands. Stipules 



usually entire 9. Pale P. 



Spikes long and slender ; the clusters of flowers, at 

 least the lower ones, distinct. 

 Perianth covered with raised dots. Taste biting 10. Waterpepper P . 

 Perianth without raised dots. Taste not biting . 11. Slender P. 



The tall Persicaria of our gardens is an east Asiatic Polygonum (P. 

 orientate), and several other Asiatic species have been recently intro- 

 duced into our flower-gardens. The Buckwheat of agriculturists, 

 occasionally found on the margins of fields where it had been cultivated, 

 is also an Asiatic plant, included by some in Polygonum (P. Fagojpy- 

 rum, Eng. Bot. t. 1044), by others separated into a distinct genus 

 under the name of Fagojpyrum. 



1. Knotweed Polygonum. Polygonum aviculare, Linu. 

 (Fig. 861.) 



(Eng. Bot. t. 1252. Knotgrass.) 



A much branched, wiry annual, prostrate when in the open ground, 

 erect when drawn up amongst corn or grass, often a foot or two long. 

 Stipules white and scarious, becoming ragged at the edges. Leaves 

 narrow-oblong, small, very rarely attaining an inch in length. Elowers 

 small, shortly stalked in clusters of 2 to 5 in the axils of most of the 

 leaves. Styles 3. Fruiting perianths but little more than a line long ; 

 the segments white on the edge, green in the centre. Nuts triangular, 

 seldom exceeding the perianth, not shining, and, when seen through a 

 strong glass, minutely granulated or wrinkled. 



In cultivated and waste places, almost all over the globe, from the 

 tropics to the Arctic regions. Abuudant in Britain. Fl. almost the 

 whole season. It varies much in its branches, sometimes very long and 



