1. Flowers in a stalked umbel; bracts foliaceous, usually larger than leaves..................................................................... D. caespitosa

- Flowers sessile, single; bracts shorter and narrower than leaves.......................................................................................................2

2. Early leaves 3–5 times longer than terminal leaves; corolla glabrous; ovules more than 15............................................................... D. bachtiarica

- Leaves not strongly anisophyllous; corolla hairy; ovules 3 to 10......................................................................................................3

3. Leaves entire with prominent eglandular hairs; glands sparse, minute and subsessile, or absent.....................................................4

- Leaves entire or lobed, with or without eglandular hairs; glands prominent, subsessile to stalked..................................................... the remaining 13 species: D. crista-gallii, D. diapensiifolia sensu lato, D. drabifolia, D. gaubae, D. haussknechtii, D. iranica, D. khuzistanica, D. odora, D. robusta, D. sarvestanica, D. tacamahaca, D. zagrica, D. zetterlundii

4. Leaves evenly covered with up to 0.2 mm long, straight acute hairs.............................................................................. D. michauxii

- Leaves with 0.4–0.7 mm long coarse curly hairs, forming a marginal fringe....................................................................................5

5. Leaves less than 4 mm; leaves eglandular.................................................................................................................... D. lamingtonii

- Leaves up to 10 mm; leaves with small subsessile glands....................................................................................................... D. avia