Diagnostic key for Aerva species occurring in Saudi Arabia

1. Plant monoecious (flowers hermaphrodite); outer two tepals 0.75–1.25 mm long, abruptly contracted at the tip to a distinct mucro formed by the excurrent nerve; style and stigmas 2, about as long as the ovary at anthesis........................................... Aerva lanata

1. Plant dioeciuos (flowers unisexual); outer two tepals (female flowers) 2–3 mm long, with the midrib not excurrent in a distinct mucro; style shorter than the ovary at anthesis; stigma 1, rudimentary .............................................................................................2

2. Leaves oblong to subcircular, more than 6 mm in wide; outer tepals> 2 mm long (up to 3 mm) ............................. Aerva javanica

2. Leaves linear to linear-oblong, up to 6 mm in wide; outer tepals about 2 mm long........................................................ Aerva bovei