R. D. Meikle, Flora of Cyprus 1. 1977
but supplemented and names used differing
1Aquatic herbs with stipulate, finely dissected submerged leaves; petals white or yellow only at the base; carpels transversely wrinkled
1'Terrestrial herbs; leaves exstipulate; petals usually yellow or sometimes coloured; achenes not transversely wrinkled
2Floating leaves absent; flowers usually large; peduncles generally much longer than leaves, seldom recurved
2'Floating leaves present, divided into 3-5 bluntly lobed segments; flowers rather small; peduncles often shorter than floating leaves, usually recurved
3Achenes very small, up to 1 mm long; nectary-pit pyriform
3'Achenes larger, longer than 1 mm; nectary-pit lunate
4Leaves all undivided, entire, with dentate or subentire margins
4'All or some of the leaves compound or deeply lobed
5Flowers very large, 2.5-7 cm diam.; petals often red, pink or white; anthers violet-purple
5'Flowers smaller, rarely exceeding 3.5 cm diam.; petals and anthers yellow
6Stems creeping, rooting at the nodes; perennial
6'Stems not rooting at the nodes, but sometimes diffuse or sprawling
7Flowers solitary, axillary or leaf-opposed; annual plants; flowers small and inconspicuous (except in R. marginatus and R. cornutus)
7'Flowers terminal; perennial plants; flowers usually conspicuous
8Achenes echinate or strongly muricate
8'Achenes muriculate, papillose or smooth, not echinate or strongly muricate
9Basal leaves spathulate-cuneate, dentate at apex; upper leaves with linear divisions; achenes with long slender spines; achene-margin at right angles to surface
9'Basal leaves reniform, deeply 3-7-lobed; upper leaves sometimes simple; achenes shortly echinate-muricate, with a broad flat marginal wing
10Peduncle shorter than adjacent leaf, incrassate in fruit; achenes narrowly bordered, with a short beak
10'Peduncle as long as, or longer than adjacent leaf, slender, not incrassate
11Achene narrowly bordered, and with a short (usually upturned) beak; upper leaves often simple or rather coarsely laciniate
11'Achene distinctly winged, with a prominent (often deflexed) beak; upper leaves laciniate with numerous linear-lanceolate lobes
12Inflorescence scapose, very sparsely branched, usually leafless or almost so; rootstock wholly or partly tuberous (grumose); achenes more than 2 mm long
12'Inflorescence branched, often leafy; if sparsely branched, then with achenes shorter than 2 mm (R. gracilis)
13Rootstock crowned with a "collar" of interwoven fibres (old, decayed leaf-bases); lower leaves often simple, broadly ovate-cuneate
13'Rootstock without a "collar" of fibres
14Leaves broadly reniform, palmately divided into blunt lobes; plant glabrescent, often tinged purple; petals 5-12 or more
14'Leaves deltoid, pinnately divided into small ovate or cuneate lobes; petals normally 5
15Sepals patent or adpressed to petals; tubers clavate
15'Sepals reflexed; tubers elongate-fusiform
16Achenes small, c. 1.5 mm long, with upturned beak
16'Achenes 2-4 mm long, with straight, recurved or hooked beak
17Plant glabrous or glabrescent; radical leaves broadly reniform or almost orbicular, rather leathery
17'Plant pubescent or villose; radical leaves broadly deltoid, deeply lobed or dissected, not leathery
18Radical leaves 2-3-pinnate, villose; peduncles divaricate, conspicuously incrassate in fruit; achenes forming a cylindrical head
18'Radical leaves broadly deltoid, 3-lobed or reniform, crenate and shallowly lobed; peduncles erect or ascending, not incrassate
19Achenes with a long, slender, straight or slightly recurved beak; root-tubers short, about 4-10 cm long
19'Achenes with a short, triangular or hooked beak; root-tubers elongate, 4-12 cm long, or wanting
20Radical leaves reniform, shallowly lobed; sepals not reflexed in flower
20'Radical leaves broadly deltoid, deeply 3-lobed or almost ternate; sepals reflexed in flower
21Achenes uniformly brown, without a margin; roots all fibrous, or at most slightly thickened
21'Achenes with a pale margin; roots intermixed with elongate cylindrical tubers
22Stock conspicuously swollen and corm-like; achenes finely punctate
22'Without corm-like stock; achenes smooth