Rumex hymenosepalus
Rumex britannica
Arizona dock, canaigre, canaigre dock, cañaigre dock, wild-rhubarb
great water dock, greater water dock, greater water or British dock, pale dock
usually erect, rarely ascending, branched above middle, 25–90(–100) cm.
erect, branched distal to middle, 80–150(–200) cm.
ocrea prominent and persistent at maturity, whitish or silvery white, membranous;
blade oblong, oblong-elliptic, or obovate-lanceolate, (5–)8–30 × 2–8(–12) cm, base cuneate or narrowly cuneate, margins entire, flat or indistinctly crisped, apex acute or acuminate, rarely obtuse.
ocrea deciduous or partially persistent at maturity;
blade lanceolate or oblong-lanceolate, normally 20–55(–70) × 2–7 cm, base cuneate, occasionally rounded or truncate, margins entire, flat to slightly crisped, apex acute.
terminal, occupying distal 1/2 of stem, narrowly paniculate, rarely simple.
terminal, occupying distal 1/2 of stem, dense or interrupted in proximal 1/2, broadly paniculate, branches usually straight or arcuate.
articulated near middle or in proximal 1/3, filiform, 5–15(–20) mm, articulation indistinct.
articulated in proximal 1/3, filiform, 5–13 mm, articulation barely evident, not distinctly swollen.
5–20 in whorls;
inner tepals oblong-cordate or orbiculate-cordate, 11–16 × 9.5–14 mm, base sinuate or emarginate, margins entire, rarely with few extremely small denticles at base, apex obtuse or subacute;
tubercles absent.
15–25 in whorls;
inner tepals orbiculate or orbiculate-ovate, rarely ovate-deltoid, 4–7(–7.5) × 3.5–7 mm, base truncate or slightly cordate, margins entire or weakly erose, flat, apex obtuse to subacute;
tubercles 3, equal or subequal, normally less than 2 times as wide as inner tepals.
brown or reddish brown, 4–5(–7) × 2.5–4.5(–5) mm.
usually reddish brown, 3–4.5 × 1.5–2.5 mm.
= 40.
= 20.
Rumex hymenosepalus
Rumex britannica
Rumex hymenosepalus is the only species of subsect. Hymenosepali Rechinger f.
Two varieties have been recognized. The typical variety has achenes 5 mm and ovate-elliptic or oblong-cordate inner tepals with a subacute apex. Variety salinus (A. Nelson) Rechinger f. has larger achenes (to 7 mm) and almost orbiculate inner tepals with an obtuse apex.
Rumex hymenosepalus was reported also from Montana (J. E. Dawson 1979), but no exact localities were given.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
The name Rumex orbiculatus commonly was applied to this North American species. After study of the Linnaean type of R. britannica, J. E. Dawson (1979) concluded that that name is the earliest valid one for this taxon.
In early North American floristic literature, Rumex britannica commonly was misidentified as R. hydrolapathum Hudson, a closely related European species also belonging to subsect. Hydrolapatha Rechinger f. (K. H. Rechinger 1937); that species differs from R. britannica in having more triangular inner tepals with an acute apex. The name R. acutus Linnaeus was misapplied to R. britannica by W. J. Hooker ([1829–] 1833–1840, vol. 2) and other botanists.
Disjunct populations have been reported from California and Louisiana. The California record (from Plumas County) was confirmed by J. E. Dawson (1979); the records from Louisiana need confirmation.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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