130 
RHEUM 
Spitzbergen, Jan Mayen Island, Nova Zembla, northern Russia, Iceland, Faeroes, Scandinavia, 
mountains of central and southern Europe ; Asia Minor ; Caucasus ; northern and central Asia ; 
North America (boreal); Greenland. Ascends to 3800m. in Switzerland. 
Tribe 2. RUMICEAE 
Rumiceae Du Mortier Anal. Fam. .18 (1829) partim ; Bentham and Hooker Gen. Plant, iii, 90 (1880); 
Dammer in Engler und Prantl Pfianzenfam. iii, pt. i, 16 (1893); Ascherson und Graebner Syn. iv, 697 (1912). 
For characters, see page 128. Only British genus: — Rumex. 
Genus 2. Rumex 
Rumex L. [Gen. PI. ed. 1, 105 (1737)] Sp. PI. 359 (1753) et Gen. PI. ed. 5, 156 (1754); Dammer in 
Engler und Prantl Pfianzenfam. iii, pt. i, 17 (1893); Ascherson und Graebner Syn. iv, 698 (1912). 
Perennial herbs, rarely biennial, with or without a sour taste. Leaves relatively narrow, as 
a rule, and pinnately nerved. Perianth dichlamydeous, more or less sepaloid, in two whorls each 
consisting of 3 segments, inner segments often enlarging in fruit and often tubercled (i.e., thickened 
towards the base of the midrib). Stamens 6, in a single whorl. Anthers basifixed. Stigmas 3, 
feathery. Achenes of 3 carpels, not winged. 
About 100 species ; temperate (especially north temperate) zones. 
We place the section Acetosa before the section Lapathum because it seems clear that the former section is more 
closely allied to Rheum , as is seen in the characters of the perianth. Doubtless, the dioecious members of the section 
Acetosa , such as Rumex acetosa and R. acetosella , have been derived from the polygamous ones. It seems to us that 
the species of Lapathum are extremely specialised, and that it is therefore proper to place them after the species of Acetosa. 
Sections of Rumex 
Section I. Acetosa (see below). Herbs with an acid taste, as in Rheum. Laminae often broad 
and hastate. Flowers polygamous or, as a rule, dioecious. Perianth somewhat petaloid. Inner 
perianth-segments not or only slightly enlarging in fruit, not or only a little tubercled. 
Section II. Lapathum (p. 133). Herbs with acid taste not pronounced or absent. Laminae 
usually relatively narrow, not hastate. Flowers polygamous or, as a rule, monoclinous. Perianth 
sepaloid. Inner perianth-segments enlarging in fruit (and then termed fruiting segments), persistent, 
clasping the achene, usually more or less tubercled. 
Section I. ACETOSA 
Acetosa [Tournefort Inst. 510, t. 290 (1719) partim, as a genus] Meisner in DC. Prodr. xiv, 64 (1856) in- 
cluding Acetosella p. 63; Bentham and Hooker Gen. Plant, iii, 101 (1880); Rouy FI. France xii, 82 (1910) inch 
Acetosella p. 81 ; Ascherson und Graebner Syn. iv, 765 (1912) incl. Acetosella p. 782. 
This section, which perhaps ought to be elevated to the rank of a subgenus, is intermediate in many respects between 
Rheum and the section Lapathum. There is more reason for separating Acetosa as a genus from Rumex than there 
is for separating Oxyria from Rheum. 
For characters, see above. 
British series of Acetosa 
Series i. # Scutati (see below). Laminae usually at least as broad as long. Flowers polygamous. 
Perianth with outer segments ultimately reflexed ; inner segments enlarging in fruit, larger than 
and enclosing the achene. 
Series ii. Acetosae (p. 13 1). Laminae usually longer than broad. Flowers mostly dioecious. 
Perianth with outer segments early becoming reflexed ; inner segments enlarging in fruit, larger 
than and enclosing the achene. 
Series iii. Acetosellae (p. 132). Laminae longer than broad. Flowers mostly dioecious. 
Perianth with all the segments applied to the achene, segments scarcely enlarging in fruit. 
Series i. * Scuta ti 
Scutati nobis. 
For characters, see above. 
