POLYGONUM 
109 
A third subfamily ( Coccolobioideat Dammer op. cit. pp. 8 et 30 (1893)), having the endosperm fissured, is not British. 
We place the Polygonoideae before the Rutnicoideae as we regard the heterochlamydeous and cyclically arranged perianth 
of the latter group, as well as its anemophilous habit and its unusual fruit-characters, as indicating that it is more specialised 
and less primitive than the former. 
Subfamily 1. POLYGONOIDEAE 
Polygonoideae Dammer in Engler und Prantl Pflanzenfam. iii, pt. 1 a, 8 (1893); Ascherson und Graebner 
Syn. iv, 798 (1912). 
For characters, see page 108. Only British genus: — Polygonum. 
Genus 1. Polygonum 
Polygonum [Tournefort Inst. 510, t. 290 (1719) incl. Persicaria p. 509, t. 290, et Fagopyrum p. 51 1, t. 290, 
et Bistorta p. 5 1 1 , t. 291] L. Sp. PL 359 (1753) et Gen. PI. ed. 5, 170 (1754); Dammer in Engler und Prantl 
Pflanzenfam. iii, pt. i a, 25 (1893); Ascherson und Graebner Syn. iv, 800 (1912). 
Undershrubs (rarely), or perennial or annual herbs. Leaves usually smaller than in Rumex, 
with ochreae which sometimes enclose cleistogamous flowers. Flowers entomophilous. Bracteoles 2. 
Perianth monochlamydeous, usually petaloid, acyclic, segments 3 — 6 usually 5, subequal in size, 
gamosepalous, persistent, not enlarging much in fruit, not becoming tubercled. Stamens 5—8, 
usually 8, honey-glands often present at the bases of the stamens and alternating with them. 
Anthers versatile. Stigmas usually capitate. Achenes more or less enclosed by the persistent perianth. 
Embryo usually lateral, rarely central. 
About 150 species; cosmopolitan, but chiefly in the temperate zones. 
Sections of Polygonum 
Section I. ^Fagopyrum (see below). Annual or perennial. Stems erect. Laminae cordate at 
the base. Perianth petaloid. Stamens 8. Stigmas 3. Embryo central. Cotyledons broad, folded. 
Section II. Tiniaria (p. no). Annual or perennial. Stem usually twining. Ochreae truncate, 
upper margin entire. Laminae cordate at the base. Inflorescence axillary. Perianth more or 
less sepaloid, sometimes becoming keeled or winged in fruit. Stamens 8. Style short. Achenes 
triquetrous. Cotyledons narrow, flat. 
Section III. # Echinocaulon (p. 112). Annual herbs. Stem weak, 4-gonous, with reflexed 
prickles. Ochreae truncate. Petioles long. Laminae cordate at the base. Perianth petaloid. 
Stamens 5 — 8. Styles as long as the stigmas. Stigmas 2 — 3. Achenes lenticular or triquetrous. 
Cotyledons accumbent, thin, flat. 
Section IV. Bistorta (p. 112). Perennial herbs with rhizomes. Aerial stem erect, unbranched. 
Ochreae truncate at the top. Petioles long. Laminae often oblong. Inflorescence terminal, spicate, 
cylindrical, dense-flowered. Perianth petaloid. Stamens 8. Styles long. Achenes triquetrous. Coty- 
ledons thin, flat, accumbent. 
Section V. Persicaria (p. 114). Annual or rarely perennial herbs. Stems erect or decumbent. 
Ochreae truncate, subentire. Petioles very short or distinct. Inflorescences spicate. Pedicels jointed 
at the top. Perianth petaloid. Flowers sometimes cleistogamous. Stamens 4 — 8. Filaments filiform. 
Achenes trigonous or bilaterally compressed. Cotyledons accumbent, thin, flat. 
Section VI. Centinode (p. 122). Perennial or annual herbs. Stems prostrate or ultimately 
decumbent, rarely remaining erect, striate. Ochreae ultimately more or less silvery or membranous, 
ultimately lacerate, sometimes containing cleistogamous flowers. Petioles very short. Inflorescences 
axillary, few-flowered. Pedicels jointed at the top. Perianth petaloid. Stamens 5 — 8. Inner 
filaments broad at the base. Achenes trigonous or subtrigonous. Cotyledons incumbent, thin, flat. 
Section I. *FA G OP YR UM 
Fagopyrum [Tournefort Inst. 51 1, t. 290 (1719) as a genus, partim] Meisner Monogr. Polyg. 43 et 61 
(1826); Dammer in Engler und Prantl Pflanzenfam. iii, pt. i a, 29 (1893) as a genus; Rouy FI. France xii, 92 
(1910). 
For characters, see above. Only British species: — *P. fagopyrum. 
