J. R. Press, Intraspecific variation in Rumex bucephalophorus L. in Bot. J. Linn. Soc. 97. 1988M. Zohary, Flora Palaestina 1. 1966R. D. Meikle, Flora of Cyprus 2. 1985T. G. Tutin, N. A. Burges, A. O. Chater, J. R. Edmondson, V. H. Heywood, D. M. Moore, D. H. Valentine, S. M. Walters & D. A. Webb, Flora Europaea 1, ed. 2. 1993
This new key needs further testing.
1Leaves hastate or sagittate
1'Leaves not hastate or sagittate
2Inner perianth segments not accrescent in fruit, not or little larger than the nut
2'Inner perianth segments accrescent in fruit, larger than the nut
3Margins of fruiting valves spinulose or rarely subentire, with marginal vein; valves distinctly unequal
3'Margins of fruiting valves entire, without marginal vein; valves subequal
4Valves entire, sometimes denticulate, but without conspicuous teeth
4'Valves conspicuously dentate, with teeth at least 0.5 mm long
5Tubercles occupying the greater part of the surface of the valve; panicles with rather long divaricate branches; leaves more or less flat
5'Tubercles inconspicuous, occupying less than one third of the width of the valve; leaves conspicuously crisp-undulate
6Plants annual, to about 30 cm high (usually much smaller); valves 2-4 mm long; fruiting pedicel often flattened or dilated
6'Plants up to 150 cm high, annual or perennial, if less than 30 cm, then perennial; valves 3-8 mm long; fruiting pedicel terete
7Valves broadly triangular, leathery, with 2(-3) stout, broadly-based teeth on each margin
7'Valves lingulate and entire, or narrowly triangular with (2-)3-4 slender teeth on each margin
8Valves clearly dentate in fruit, the teeth at least 1 mm long
8'Valves entire or denticulate in fruit, the teeth rarely as much as 1 mm long
9Annual; inflorescence simple and spiciform, or with lax, erect or ascending branches; valves 3-4 mm wide
9'Perennial; inflorescence a lax panicle, with long, spreading branches; valves 4-7 mm wide -- go to key point 11
10Branching not strongly divaricate, becoming rather crowded; pedicels thin, longer than perianth segments; margins of fruiting valves irregularly erose-denticulate; largest callus 2-3 x 1.5 mm
10'Branching strongly divaricate; pedicels thick, about as long as perianth segments; margins of fruiting valves pectinate-spinulose, occasionally subentire; largest callus c. 2 x 1 mm
11Valves entire, or with a few teeth not more than 0.5 mm long near the base
11'Valves with several teeth on each margin; teeth more than 0.5 mm long
12Valves broadly deltoid or suborbicular, 6-7 x 6-7 mm; teeth short, up to 8 on each margin
12'Valves narrowly ovate, oblong or oblong-deltoid with lingulate apex, less than 6 mm wide; 4-6 teeth on each margin
13Valves c. 6 mm long; teeth 3-4 mm long, 5-6 on each margin
13'Valves 4-6 mm long; teeth 1-2 mm long, sometimes longer, 4 on each margin
14Inflorescence much branched; valves 4-5 mm long; teeth 1-2 mm long; basal leaves usually panduriform
14'Inflorescence unbranched or with few, elongate branches; valves 4-6 mm long; teeth 1-2 mm long or longer; leaves not panduriform