2Sepals 5; leaves sometimes becoming alternate on flowering stems3
3Plant finely papillate (papillae on young stems c. 0.5 mm diam.); stems angular; sepals conspicuously keeled; petaloid staminodes subequal to sepalsMesembryanthemum aitonis
3Plant coarsely papillate (papillae on young stems 1–2 mm diam.); stems terete or angular; sepals not keeled; petaloid staminodes much exceeding sepals4
4Plant annual; ± prostrate, to 20 cm high, spreading; stem terete; pedicel 0–5(–12) mm long; flowers 10–20(–30) mm diam. receptacle c. 8 mm diam., sepals 4–8 mm longMesembryanthemum crystallinum
4Plant annual or biennial (possibly annual under adverse conditions); plant with an erect central stem 30–60(–100) cm high; stem angled-ribbed; pedicel 20–30 mm long; flowers (15–)49–60(–70) mm diam.; receptacle 12–15 mm diam.; sepals 9–12 mm longMesembryanthemum guerichianum
5Plants perennial; leaves withering and soon deciduous, branches retaining only the persistent leaf bases; innermost series of staminodes gathered around the stamens, forming a coneMesembryanthemum granulicaule
5Plants annual; leaves persistent; innermost series of staminodes spreading and not forming a cone around the stamensMesembryanthemum nodiflorum
