| 1. | Inflorescence readily disarticulating at maturity | 2 |
| Inflorescence not disarticulating at maturity | 4 | |
| 2. | Racemes ±exserted from floral sheaths | I. macratherum (NT WA QLD) |
| Racemes enclosed within floral sheaths | 3 | |
| 3. | Involucral spikelets present in lowest racemes | I. vaginiflorum (NSW NT SA WA QLD) |
| Involucral spikelets absent | I. fragile (NT SA QLD) | |
| 4. | Involucral spikelets 4-6.5 mm long | 5 |
| Involucral spikelets 3-4 mm long | 10 | |
| 5. | Sessile spikelets glabrous at base | I. calvum (NT QLD) |
| Sessile spikelets hairy at base | 6 | |
| 6. | Lower glume of involucral spikelet ciliate on keels | I. ciliatum (NT WA QLD) |
| Lower glume of involucral spikelet minutely scabrid on keels | 7 | |
| 7. | Inflorescence sparse; peduncles very long and slender | I. holmesii (WA) |
| Inflorescence ±dense; peduncles short | 8 | |
| 8. | Floral sheaths not glandular on keel; involucral spikelets 4-5 mm long | I. convexum (NT QLD) |
| Floral sheaths glandular on keel; involucral spikelets 5-6.5 mm long | 9 | |
| 9. | Hairs of raceme base 2-3 mm long | I. windersii (NT QLD) |
| Hairs of raceme base c. 4.5 mm long | I. trichopus (NT WA) | |
| 10. | Pedicels of involucral spikelets bearded throughout | I. dolichotrichum (NT WA QLD) |
| Pedicels of involucral spikelets bearded only at base | 11 | |
| 11. | Raceme base with hairs to 1.5 mm long or glabrous | I. membranaceum (NSW NT SA WA QLD) |
| Raceme base with hairs 2-5 mm long | I. eremaeum (NT SA WA QLD) |
Key to Iseilema derived from Hubbard 1935c; Blake 1938
Taxonomic name: