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Specimen numbers are hyperlinked to records in the Consortium of California Herbaria data view where possible. Taxa are hyperlinked to entries in the Jepson Interchange via the "[Online Interchange]" link.

 

MUHLENBERGIA MUHLY

Paul M. Peterson


Annual, perennial herb, occasionally mat-like, often rhizomed. Stem: decumbent to erect, ± clumped. Leaf: basal and cauline; sheath open; ligule membranous, entire to irregularly toothed, occasionally with 1 large tooth on each side; blade flat to rolled. Inflorescence: panicle-like, narrow to open; branches spreading to appressed. Spikelet: generally single (bisexual) occasionally paired (bisexual, staminate or sterile); glumes subequal, generally 1–3-veined, short-pointed to awned, upper glume occasionally 3-veined; florets 1, occasionally 2; axis breaking above glumes; lemma short-pointed to awned, glabrous to hairy, 3-veined; palea <= lemma. Fruit: ± fusiform, red-brown, generally falling with lemma and palea.
173 species: temperate America, southern Asia. (G.H.E. Muhlenberg, Pennsylvania botanist, 1753–1815) {hort link} Reports of Muhlenbergia dumosa Vasey, Muhlenbergia glauca (Nees) B.D. Jacks., Muhlenbergia thurberi (Scribn.) Rydb. have proved to be erroneous.
Unabridged references: [Peterson 2003 FNANM 24:145–200; Reeder 1981 in Gould and Moran 1981 San Diego Soc Nat Hist Memoir 12:67–78]

Key to Muhlenbergia

1. Annual

2. Lemma awned, awn 1–3 cm, lemma 2.5–6 mm

3. Lemma generally 4.5–6 mm; inflorescence generally < 1.5 cm wide, branches closely appressed; glumes generally 1–2 mm ..... M. appressa

3' Lemma generally 2.5–4.5 mm; inflorescence 1–5 cm wide, branches spreading to ascending; glumes generally < 1 mm ..... M. microsperma (2)

2' Lemma short-awned, awn < 1 mm, or awn 0; lemma < 2.5 mm

4. Inflorescence narrow, < 1 cm wide; branches closely appressed; stems often rooting at lower nodes ..... M. filiformis (2)

4' Inflorescence open, 1.5–8 cm wide; branches reflexed, ascending to spreading; stems not rooting at lower nodes

5. Inflorescence branches stiffly spreading to reflexed ± 90° from axis; glumes glabrous; ligule teeth 2, 1 on each side ..... M. fragilis

5' Inflorescence branches ascending < 80° from axis; glume tip short-hairy; ligule truncate to obtuse, irregularly short-toothed ..... M. minutissima

1' Perennial herb

6. Lemma awn 0 or short-awned, awn < 1 mm

7. Inflorescence 5–14 cm wide, open, branches spreading ..... M. asperifolia

7' Inflorescence <= 4 cm wide, narrow, branches ascending to appressed, occasionally loosely spreading

8. Rhizomes creeping, ± scaly; stems ± decumbent to erect

9. Glumes 2.5–4 mm, ± = lemma; lower 1/2 lemma short-soft-hairy ..... M. californica (2)

9' Glumes 0.5–1.8 mm, ± 1/2 lemma; lemma glabrous to ± scabrous

10. Ligule generally 1–2.5 mm; inflorescence axis generally obscured by branches, spikelets ..... M. richardsonis

10' Ligule generally < 1 mm; inflorescence axis generally visible between branches ..... M. utilis

8' Rhizomes 0; stems clumped or decumbent and ± rooting at nodes

11. Blade < 4 cm; lemma generally < 2 mm; stem generally < 3 dm ..... M. filiformis (2)

11' Blade >= 5 cm; lemma generally > 2.5 mm; stem 2–15 dm

12. Inflorescence <= 15 cm, 1.5–4 cm wide; branches loosely flowered ..... M. jonesii

12' Inflorescence 15–60 cm, <= 1.2 cm wide; branches densely flowered ..... M. rigens

6' Lemma awn 1–30 mm

13. Inflorescence open, 6–15 cm wide, branches spreading ..... M. porteri

13' Inflorescence generally < 6 cm wide, branches ascending to appressed, occasionally spreading

14. Glumes 1 or 2, generally < 0.5 mm, vein 0 ..... [M. schreberi]

14' Glumes 2, generally > 0.5 mm, vein(s) evident

15. Rhizome generally scaly, creeping

16. Blade generally rolled, < 2 mm wide; anther purple, 1.5–3 mm

17. Lemma, palea short-soft-hairy on lower 1/2; stems loosely clumped, decumbent ..... M. arsenei (2)

17' Lemma base sparsely short-hairy; palea glabrous to ± scabrous; stems erect, ± rooting at lower nodes ..... M. pauciflora (2)

16' Blade generally flat, >= 2 mm wide; anther yellow, generally <= 1.5 mm

18. Hairs at lemma base 2–3.5 mm ..... M. andina

18' Hairs at lemma base < 1.5 mm

19. Lemma awn generally < 2.2 mm; anther 1–1.5 mm ..... M. californica (2)

19' Lemma awn 2.5–9 mm; anther < 0.5 mm ..... M. mexicana

15' Rhizomes 0

20. Upper glume 3-veined, 3-toothed ..... M. montana

20' Upper glume generally 1-veined, obtuse, acute, or awned

21. Lower glume 2-veined, 2-awned; inflorescence 5–8 mm wide, spike-like, dense ..... M. alopecuroides

21' Lower glume 1-veined, with 1 awn or awnless; inflorescence 5–30 mm wide, dense to loose

22. Glumes 0.5–1 mm, obtuse; cleistogamous spikelets generally present in lowermost stem axils ..... M. microsperma (2)

22' Glumes generally 1.5–3.5 mm, acute, acuminate, or awned; cleistogamous spikelets 0

23. Lemma, palea short-soft-hairy on lower 1/2; stems loosely clumped, decumbent ..... M. arsenei (2)

23' Lemma base sparsely short-hairy; palea glabrous to ± scabrous; stems erect, ± rooting at lower nodes ..... M. pauciflora (2)

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