This new key is mostly based on the key published by Meikle (1985). The treatment of sect. Chamaesyce by Frajman (in Hand 2011) has been integrated. It includes E. humifusa, which has not been found in Cyprus yet but is to be expected.
Further testing of the key is required.
| 1 | Leaves (mostly) oblique at the base; stipules membranous (in E. graminea sometimes rudimentary); glands appendiculate |
| 1' | Leaves symmetrical at the base; stipules membranous, glandular or not; glands ex-appendiculate |
| 2 | Cyathia in capitate glomerules; ovaries and capsules strigillose |
| 2' | Cyathia more lax and not arranged in capitate glomerules; if cyathia dense and nearly globular then plant with glabrous ovaries and capsules |
| 3 | Plant ascending to erect, up to 0.6 m high; largest leaves usually longer than 15 mm; leaves alternate or opposite |
| 3' | Plant mostly prostrate, rarely ascending; the largest leaves usually up to 12(-15) mm long; leaves opposite |
| 4 | Leaves opposite; cyathia in axial and/or terminal, more or less dense clusters; seeds 0.9-1.3 mm long |
| 4' | Leaves alternate, sometimes some opposite; cyathia usually in terminal dichasia, not congested; seeds 1.5-1.7 mm long |
| 5 | Plant glabrous; stipules membranous, clearly visible, connate; terminal pseudocorymbiform cymes very dense; fruits shorter than 1.4 mm; seeds shorter than 1 mm |
| 5' | Plant at least in some parts pubescent; stipules inconspicuous, connate or free; terminal pseudocorymbiform cymes lax; fruits 1.5-2.5 mm long; seeds 1.1-1.3 mm long |
| 6 | Plant usually glabrous (E. humifusa rarely sparingly hairy); seeds smooth |
| 6' | Plant usually pubescent (E. chamaesyce can be glabrous); seeds tuberculate-rugulose or transversely furrowed |
| 7 | Plant fleshy; leaves falcate-oblong, conspicuously asymmetrical at the base (half of the limb with basal auricle); fruits 3-4 x 4-5 mm; seeds 2.5-3 mm long; plants of sandy coastal areas |
| 7' | Plant not fleshy; leaves not conspicuously asymmetrical at the base; fruits 1.2-1.8 mm long and wide; seeds up to 1.3 mm long; plants of ruderal places |
| 8 | Stems never rooting at nodes; leaves oblong-ovate to oblong-obovate, serrulate at least in upper part, apex rounded; stipules filiform; seeds ovoid |
| 8' | Stems often rooting at nodes; leaves ovate to suborbicular, margin entire, apex retuse to emarginate; stipules united into a triangular, laciniate or fimbriate white scale; seeds tetrahedral |
| 9 | Plant somewhat glaucous; leaves ovate-suborbicular; fruit with patent hairs or glabrous, 1.5-1.9 x 1.6-2 mm; seeds irregularly tuberculate-rugulose, 1-1.4 x (0.6-)0.7-0.9 mm |
| 9' | Plant not glaucous; leaves oblong to elliptical or obovate-oblong; fruit appressed-pubescent or hairy only on the keels, 1-1.5(-1.6) x 1-1.5 mm; seeds regularly transversely furrowed, 0.8-1.1 x 0.4-0.6(-0.7) mm |
| 10 | Leaves on the upper surface mostly with prominent purple spot; stipules linear-lanceolate to filiform, 0.8-1.3 mm long; fruit (all surface) appressed-pubescent |
| 10' | Leaves on the upper surface mostly without prominent purple spot; stipules mostly connate at base, triangular-subulate, 0.5-1 mm long; fruit pilose only along the keels |
| 11 | Stipules membranous, minute; leaves spinulose-denticulate, densely wooly, petiolate; glands pectinate |
| 11' | Stipules glandular or not; leaves entire or serrate, variously indumented, usually sessile; glands entire or 2-horned |
| 12 | Stipules glandular; cyathia with 1-2(-3) glands |
| 12' | Plant without stipules; cyathia with 4-5 glands |
| 13 | Glands rounded on the outer edge |
| 13' | Glands truncate, lunate or 2-horned |
| 14 | Perennial herbs or shrubs |
| 14' | Annuals |
| 15 | Plants with a napiform root-tuber; autumn-flowering |
| 15' | Plants without a root-tuber; spring- or summer-flowering |
| 16 | Seeds minutely tuberculate |
| 16' | Seeds smooth or shallowly pitted |
| 17 | A shrub; regma verrucose |
| 17' | Perennial herbs; regma smooth |
| 18 | Stems stiffly erect; cauline- and ray-leaves 1-2 mm wide; seeds pale grey |
| 18' | Stems prostrate or decumbent-ascending; cauline- and ray-leaves 2-4 mm wide; seeds brownish |
| 19 | Seeds smooth |
| 19' | Seeds variously ornamented or sculptured |
| 20 | Leaves finely serrulate; regma beset with subulate processes |
| 20' | Leaves coarsely serrate; regma smooth |
| 21 | Regma villose |
| 21' | Regma smooth |
| 22 | Leaves serrulate; seeds brown, with a flat caruncle |
| 22' | Leaves coarsely serrate; seeds black, with a protuberant caruncle |
| 23 | Annuals; seeds variously ornamented or sculptured |
| 23' | Perennials; seeds smooth |
| 24 | Seeds tuberculate or rugulose |
| 24' | Seeds pitted or grooved or both |
| 25 | Lower cauline leaves densely imbricate, linear-setaceous |
| 25' | Lower cauline leaves laxly arranged, linear to linear-oblanceolate |
| 26 | Cauline leaves petiolate; regma-valves 2-ridged |
| 26' | Cauline leaves sessile or subsessile; regma-valves smooth |
| 27 | Seeds longitudinally grooved and pitted |
| 27' | Seeds transversely grooved |
| 28 | Glands usually long-horned; regma 2.5-3 mm diam.; seeds ovoid, pitted or reticulate |
| 28' | Glands short- or medium-horned or almost hornless; regma 1.5 mm diam.; seeds dorsiventrally compressed, transversely grooved or pitted |
| 29 | Raylet-leaves as long as or longer than broad, lax, with mucro 1-1.5 mm long; seeds 1-2 mm long, with (4-)5-7 transverse grooves per facet |
| 29' | Raylet-leaves as broad as or broader than long, densely imbricate, with arista (1-)2-3 mm long; seeds 1.5-2 mm long, with (5-)9-15 transverse grooves or pits per facet |
| 30 | Regma triquetrous, the valves angled |
| 30' | Regma trilobate, the valves rounded |
| 31 | Plant very fleshy; leaves adaxially concave; caruncle minute |
| 31' | Plant not fleshy; leaves flat; caruncle prominent |
| 32 | Lower cauline leaves more or less equalling the upper; raylet-leaves free |
| 32' | Lower cauline leaves much larger than the upper; raylet-leaves connate |
