| | 1. Glumes deciduous; spikelets falling as 1 unit, 1–2 per inflorescence branch (sect. Melica) |
| M. stricta |
| | 1' Glumes persistent; spikelet axis breaking above glumes, spikelets > 2 per lower inflorescence branch (sect. Bromelica) |
| |
| | 2. Lemma acuminate or awned; hairs (if any) near base |
| |
| | 3. Awn 5–12 mm; lemma surface glabrous, margin often hairy near base |
| M. aristata |
| | 3' Awn 0–4 mm; lemma surface hairy near base |
| |
| | 4. Lemma obtuse to ± tapered, awn 1–4 mm, ciliate; corms 0 |
| M. harfordii |
| | 4' Lemma strongly tapered, awn 0; corms present |
| M. subulata |
| | 2' Lemma obtuse to acute, awn 0, hairs (if any) near tip |
| |
| | 5. Fertile florets 1–2 in all spikelets |
| |
| | 6. Sterile cluster at axis tip 0.5–4 mm, widest at middle or below; lemma glabrous or minutely scabrous |
| M. imperfecta |
| | 6' Sterile cluster at axis tip 0.5–1.5 mm, truncate or widest above middle; lemma margin generally hairy |
| M. torreyana |
| | 5' Fertile florets 3–7 in some or all spikelets |
| |
| | 7. Stem 10–60 cm; floret stalks swollen when fresh, ± wrinkled and yellow-brown when dry |
| M. fugax |
| | 7' Stem 45–200 cm; floret stalks not swollen nor wrinkled when dry |
| |
| | 8. Palea 1/2–3/4 × lemma length; leaves 3–5 per stem, blades 3–9 cm |
| M. frutescens |
| | 8' Palea ± 7/8 × lemma length; leaves 2–3 per stem, blades generally >> 9 cm |
| |
| | 9. Sterile cluster at axis tip widest above middle, tip truncate |
| M. californica |
| | 9' Sterile cluster at axis tip widest below middle, tip acute to acuminate |
| |
| | 10. Both glumes ± 1/2 lowest floret length; corms connected to rhizome by short stalk |
| M. spectabilis |
| | 10' 1 or both glumes ± 3/4 lowest floret length; corms sessile on rhizome (or rhizome 0) |
| |
| | 11. Sheath of basal leaf remaining intact; inflorescence ± narrow, branches ± ascending |
| M. bulbosa |
| | 11' Sheath of basal leaf becoming fibrous; inflorescence generally wide, branches spreading to reflexed |
| M. geyeri
|