128 
RHEUM 
British tribes of Rumico'ideae 
Tribe i. Rhabarbareae (see below). Flowers monoclinous or polygamous, entomophilous. 
Perianth usually more or less petaloid, segments 4 — 6. Stamens 6 — 9, in two whorls. Anthers 
versatile. Achenes usually not enclosed by the persistent calyx, bifacial or triquetrous, with a 
membranous wing at each angle. Embryo axile. 
Tribe 2. Rumiceae (p. 130). Flowers monoclinous, polygamous, or dioecious. Perianth 
usually sepaloid, segments 6, in two whorls of 3 segments each. Stamens usually 6, in a single 
whorl. Anthers basified. Achenes often enclosed by persistent perianth-segments. Embryo lateral 
or rarely axile. 
Tribe 1. RHABARBAREAE 
Rhabarbareae Meisner in DC. Prodr. xiv, 30 (1856) as a subtribe; Ascherson und Graebner Syn. iv, 
789 (1912). 
For characters, see above. Only British genus : — Rheum. 
Genus 1. Rheum 
Rheum L. [Gen. PI. 120 (1737)] Sp. PI. 371 (1753) et Gen. PI. ed. 5, 174 (1754); Wahlenberg Ft. Lapp. 
101 (1812); Ascherson und Graebner Syn. iv, 791 (1912) including Oxyria. [Rhabarbarum Tournefort Inst. 89, 
t. 18 (1719) including Acetosa partim.] 
Perennial herbs, with a sour taste. Leaves relatively broad, palmatinerved, with ochreae. 
Perianth dichlamydeous, more or less petaloid, in two whorls each consisting of n segments, 
not enlarging much in fruit, not tubercled. Stamens 2 n + n, outer whorl antisepalous, inner whorl 
antipetalous, introrse. Stigmas n, feathery. Achenes of n carpels, with n wings. ( n is usually 
3, rarely — as in the British species — 2.) 
When founding the genus Oxyria , Hill (loc. cit.) remarked that “this is a perfectly artificial genus. Nature declares 
the plant to be a kind of sorrel [or Acetosa] ; but the structure of its flower [which Hill did not understand] requires 
its being also here.” Having founded a genus for the reception of its only species, it would be expected that Hill 
would place the species in that genus. Instead of doing so, however, Hill (op. cit. p. 24) described the plant under 
its Linnaean name Rumex digynus, and repeated this (op. cit. p. 41) when dealing in the same volume with the 
genus Rumex. It cannot be denied that this is a poor beginning for any genus. Even when Hill does actually name 
the plant Oxyria digyna (in Hort. Kew. p. 158 (1769)), the appellation is virtually a nomen nudum, there being no 
description but only a footnote adding '•'•Rumex digynus auctorum.” Thus both the genus Oxyria and its only species 
begin their respective lives under highly adverse circumstances. 
When Smith (Eng. Ft. ii, pp. 188 — 189 (1824)) took up Hill’s genus, he remarked: — “Sir John Hill, it seems, 
first separated this plant from Rumex ” ; but this ignores Miller, who (Gard. Did. ed. 8, no. 4 (1768)) named the 
plant Acetosa digyna the year before the publication of the name Oxyria digyna. Referring to Hill, Smith continues : — 
“Sometimes, as Linnaeus says, a blind hen meets with a grain of corn.” In our opinion, this grain of corn was really 
only a husk, the kernel having aborted, as the botanical differences between Oxyria and the Linnaean genus Rheum 
are of no importance. 
Oxyria has the parts of its flowers in 2’s, Rheum in 3’s; and thus Wahlenberg (loc. cit.) was justified in placing 
the plant in the latter genus. The case is analogous with Tillaea and Crassula ; and Tillaea was reduced to Crassula 
by Schonland in Pflanzenfamilien iii, pt. 2 a, 77 (1891). 
Tournefort (loc. cit.) placed the plant in his pre-Linnaean genus Acetosa. Linnaeus (loc. cit.) reduced the two Tournefortian 
genera Acetosa and Lapathum to Rumex, but erred in referring the plant to Rumex. The resemblance of the androecium of 
the plant to that of Rumex is merely superficial : both have 6 stamens, it is true ; but the arrangement of these is quite 
different, as is shown in our descriptions. 
If the plant be not placed in the genus Rheum, it is a nice question for nomenclators whether or not Acdosa has prior 
claim to Oxyria. 
About 40 species, chiefly Asiatic. Only British species : — R. digynum. 
I. RHEUM DIGYNUM. Mountain Sorrel. Plate 137 
Acetosa cambro-britannica montana Parkinson Theatr. Bot. 745 (1640); A. rotundifolia repens eboracensis 
folio in medio deliquium patiente Morison Hist. Oxon. 583 (1672); Ray Syn. ed. 3, 143 (1724). 
Rheum digynum Wahlenberg Ft. Lapp. 101 , t. 9, fig. 2 (1812); Rumex digynus L. Sp. PL 337 (1753)!; 
Hill Veg. Syst. x, 24 et 41 (1765); Smith Ft. Brit. 395 (1800)!; Acetosa digyna Miller Gard. Diet. ed. 8, no. 4 
(1768); Oxyria digyna Hill Hort. Kew. 158 (1769); Rouy Ft. France xii, 68 (1910); Ascherson und Graebner 
Syn. iv, 790 (1912); Oxyria reniformis Hooker Ft. Scot, i, 111 (1821); Smith Eng. Ft. ii, 188 (1824); Syme Eng. 
Bot. viii, 57 (1868). 
