14. POEAE R. Br.
Mary E. Barkworth

Plants annual or perennial; cespitose, rhizomatous, or stoloniferous. Culms annual, not woody, not branching above the base; internodes usually hollow. Sheaths usually open for most of their length, sometimes closed; collars without tufts of hair on the sides; auricles usually absent; ligules membranous to hyaline, sometimes ciliate, those of the upper and lower cauline leaves usually similar; pseudopetioles not developed; blades linear to narrowly lanceolate, venation parallel, cross venation not evident, without arm or fusoid cells, epidermes without microhairs, not papillate, cross sections non-Kranz. Inflorescences terminal, usually panicles, sometimes spikes, panicles sometimes spikelike or reduced to racemes in depauperate specimens; disarticulation usually above the glumes and beneath the florets, sometimes below the glumes. Spikelets 0.7–50 mm, laterally compressed, sometimes weakly so, sometimes viviparous, usually with 2–22 florets, sometimes with 1, sterile florets usually distal to the reproductively functional florets, sometimes with 1 or 2 staminate or sterile florets below a bisexual floret, sterile florets often reduced in size; rachillas sometimes prolonged beyond the base of the distal florets. Glumes (0,1)2, equal or unequal, shorter or longer than the adjacent florets, sometimes exceeding the distal florets; florets laterally compressed; calluses glabrous or hairy, not well developed; lemmas lanceolate to ovate, 1–7(9)-veined, unawned or awned, veins usually converging distally, sometimes parallel, awns from basal to terminal on the lemmas, straight or bent; paleas 2-keeled, from shorter than to longer than the lemmas, sometimes absent or minute; lodicules 2, membranous, not or weakly veined; anthers 3; ovaries usually glabrous, sometimes hairy distally; styles 2, bases free. Caryopses longitudinally grooved or not, not beaked, pericarp thin; hila punctate to linear; embryos from 1/4–1/3 as long as the caryopses. x = 7.

The Poeae constitute the largest tribe of grasses, encompassing around 115 genera and 2500 species. The species are primarily cool-temperate to arctic in their distribution. In the Flora region, there are 63 non-hybrid genera with 344 species, and 4 hybrid genera, each of which has one species. Many of the tribe’s species are well known as lawn and pasture grasses, for example, Poa pratensis (Kentucky bluegrass), Dactylis glomerata (orchard grass), and Phleum pratense (timothy).

The tribe’s circumscription and its infratribal taxonomy are unclear. It is interpreted here as including generic groups that are, or have been, treated in other works as tribes (e.g., Agrostideae Dumort., Aveneae Dumort., Hainardeae Greut., and Phalarideae Dumort.). Some of these are sometimes recognized as subtribes, often with modified circumscriptions. Recent studies (e.g., Catalán et al. 1997, 2004; Soreng and Davis 1998) indicate that there are some infratribal groupings that, based on chloroplast DNA data, appear stable; other groupings do not. In addition, there is little support for the monophyly of some genera, notably Festuca and its allies.

The following key does not include these four hybrid genera: ×Agropogon (Agrostis × Polypogon), ×Arctodupontia (Arctophila × Dupontia), ×Dupoa (Dupontia × Poa), and ×Pucciphippsia (Puccinellia × Phippsia). They are described on the pages indicated. In the key that follows, branch measurements include spikelets, but not awns.

SELECTED REFERENCES Catalán, P., E.A. Kellogg, and R.G. Olmstead. 1997. Phylogeny of Poaceae subfamily Poöideae based on chloroplast ndhF gene sequences. Molec. Phylogenet. Evol. 8:150–166; Catalán, P., P. Torrecilla, J.Á. López Rodríguez, and R.G. Olmsted. 2004. Phylogeny of the festucoid grasses of subtribe Loliinae and allies (Poeae, Poöideae) inferred from ITS and trnL–F sequences. Molec. Phylogenet. Evol. 31:517–541; Macfarlane, T.D. 1987. Poaceae subfamily Poöideae. Pp. 265–276 in T.R. Soderstrom, K.W. Hilu, C.S. Campbell and M.E. Barkworth (eds.). Grass Systematics and Evolution. Smithsonian Institution Press, Washington, D.C., U.S.A. 473 pp.; Soreng, R.J. and J.I. Davis. 1998. Phylogenetics and character evolution in the grass family (Poaceae): Simultaneous analysis of morphological and chloroplast DNA restriction site character sets. Bot. Rev. (Lancaster) 64:1–85.; Soreng, R.J., J.I. Davis, and J.J. Doyle. 1990. A phylogenetic analysis of chloroplast DNA restriction site variation in Poaceae subfam. Poöideae. Pl. Syst. Evol. 172:83–97.

 

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1. All or almost all spikelets viviparous, the spikelets producing plantlets [if sexual spikelets are common, take the alternate lead] ... (2)
1. Some, usually all, spikelets sexually functional, with 1–25 bisexual or unisexual florets, sometimes with sterile and sexual spikelets mixed within an inflorescence ... (4)
2. Panicle branches smooth or slightly scabrous, the scabrules widely spaced; blades with a translucent line on either side of the midvein, apices usually prowlike ... Poa (in part)
2. Panicle branches scabrous; blades without a translucent line on either side of the midvein, apices usually not prowlike ... (3)
3. Sheaths closed for 1/2 or more of their length; ligules 0.1–0.6 mm long ... Festuca (in part)
3. Sheaths open; ligules 1.5–13 mm long ... Deschampsia (in part)
4. Inflorescences with 2 morphologically distinct forms of spikelets ... (5)
4. Inflorescences with all spikelets morphologically alike ... (7)
5. Spikelets in pairs, the pedicels not fused at the base, smooth or slightly scabrous; disarticulation above the glumes and beneath the florets ... Cynosurus
5. Spikelets in fascicles, the pedicels fused at the base, glabrous, hispid or strigose; disarticulation at the base of the fused pedicels ... (6)
6. Secondary panicle branches sharply bent below the pedicels; glumes not winged ... Lamarckia
6. Secondary panicle branches straight below the pedicels; glumes winged ... Phalaris (in part)
7. Glumes with pilose awns ... Lagurus
7. Glumes, if present, unawned or with glabrous awns ... (8)
8. Inflorescences spikes with 1–2(4) spikelets per node, or spikelike racemes with 1 spikelet at all or most nodes ... (9)
8. Inflorescences panicles or racemes, with more than 1 spikelet associated with each node ... (19)
9. Spikelets with 1 functional floret, sometimes a reduced, sterile floret also present ... (10)
9. Spikelets with 2–25 functional florets ... (13)
10. Glumes membranous, flexible; all spikelets pedicellate, pedicels 0.5–1 mm long, 0.1–0.2 mm thick ... Mibora
10. Glumes coriaceous, stiff; lower spikelets sessile, upper spikelets sometimes pedicellate ... (11)
11. Spikelets radial to the rachises, most spikelets with 1 glume, the terminal spikelets with 2 glumes ... Hainardia
11. Spikelets tangential to the rachises, all with 2 glumes ... (12)
12. Lemmas unawned ... Parapholis
12. Lemmas awned, awns 2–4 mm ... Scribneria
13. Lemmas awned from about midlength, awns 8–26 mm long, twisted proximally ... (14)
13. Lemmas unawned or apically awned, awns straight ... (15)
14. Adaxial surfaces of the leaves ribbed; rachillas pilose on all sides; ligules truncate to rounded, 0.5–1.5 mm long ... Helictotrichon (in part)
14. Adaxial surfaces of the leaves unribbed; rachillas glabrous on the side adjacent to the paleas, hairy elsewhere; ligules acute to truncate, 0.5–7 mm long ... Avenula (in part)
15. Spikelets sessile; lemmas 2–12 mm long ... (16)
15. Spikelets subsessile to pedicellate, pedicels 0.5–3 mm long ... (17)
16. Spikelets radial to the rachises, most spikelets with 1 glume, only the terminal spikelet with 2 glumes ... Lolium
16. Spikelets tangential to the rachises, all spikelets with 2 glumes ... Gaudinia
17. Plants perennial ... Festuca (in part)
17.Plants annual ... (18)
18. Inflorescences usually exceeded by the leaves; spikelets with (2)3–4(7) florets; lemmas (5)7–9-veined, apices round to emarginate, not bifid; culms usually prostrate or procumbent ... Sclerochloa (in part)
18. Inflorescences usually exceeding the leaves; spikelets with 4–25 florets; lemmas 5-veined, apices acute to obtuse, sometimes bifid; culms procumbent to erect ... Desmazeria (in part)
19. Inflorescences racemes or spikelike panicles, with all branches shorter than 1 cm ... (20)
19. Inflorescences panicles, dense to open, sometimes compact, usually at least some branches longer than 1 cm ... (39)
20. Leaves usually exceeding the inflorescences; culms usually prostrate to procumbent; lemmas indurate at maturity ... Sclerochloa (in part)
20. Leaves usually exceeded by the inflorescences; culms usually erect or decumbent at the base; lemmas usually membranous or papery, sometimes coriaceous, not indurate ... (21)
21. Spikelets disarticulating below the glumes or, if the spikelets are attached to stipes, at the base of the stipes; glume bases sometimes fused ... (22)
21. Spikelets disarticulating above the glumes; glume bases not fused ... (24)
22. Spikelets weakly laterally compressed, with stipes that fall with the spikelets; glume bases not fused; glumes usually awned ... Polypogon (in part)
22. Spikelets strongly laterally compressed, without stipes; glume bases sometimes fused; glumes unawned or awned ... (23)
23. Lemmas dorsally awned; spikelets oval in outline; glumes often connate at the base, often winged distally, keels sometimes ciliate, apices never abruptly truncate ... Alopecurus (in part)
23. Lemmas usually unawned, occasionally subterminally awned; spikelets often U-shaped in outline, sometimes oval; glumes not connate at the base, not winged, often strongly ciliate on the keels and abruptly truncate to an awnlike apex ... Phleum (in part)
24. Spikelets with 2–25 bisexual florets, the sterile or staminate florets, if present, distal to the bisexual florets ... (25)
24. Spikelets with 1 bisexual floret, sometimes with 1–2 sterile florets below the bisexual floret, the sterile florets sometimes reduced to lemmas, sometimes resembling tufts of callus hair ... (30)
25. Sheaths closed for at least 1/2 their length ... (26)
25. Sheaths open for all or almost all of their length ... (27)
26. Lemma midveins sometimes excurrent up to 2.2 mm, other veins not excurrent; plants native, arctic ... Dupontia (in part)
26. Lemmas with 3–5 veins excurrent, forming awnlike teeth; plants cultivated ... Sesleria
27. Distal lemmas, sometimes all lemmas, awned from below midlength ... Aira (in part)
27. All lemmas unawned or apically awned ... (28)
28. Lemmas coriaceous at maturity, unawned, sometimes mucronate ... Desmazeria (in part)
28. Lemmas membranous, apically awned, awns 0.3–22 mm long ... (29)
29. Lemma margins involute, not scarious ... Vulpia (in part)
29. Lemma margins flat, scarious ... Rostraria (in part)
30. Spikelets with 1–2 sterile or staminate florets below the bisexual florets, these from larger than to much smaller than the bisexual florets, sometimes resembling tufts of hair; glumes sometimes winged distally ... (31)
30. Spikelets without sterile or staminate florets below the bisexual floret; glumes not winged distally ... (32)
31. Fresh leaves not sweet-smelling when crushed; sterile lemmas unawned; bisexual lemmas usually hairy, sometimes sparsely so; glumes subequal, sometimes winged distally ... Phalaris (in part)
31. Fresh leaves sweet-smelling when crushed; sterile lemmas awned; bisexual lemmas glabrous; glumes unequal, not winged ... Anthoxanthum (in part)
32. Lemmas dorsally awned, awns geniculate; lateral lemma veins excurrent, forming 4 teeth, teeth sometimes awnlike ... Bromidium (in part)
32. Lemmas unawned or with only 1 awn, awns not strongly geniculate; lateral lemma veins not excurrent ... (33)
33. Spikelets 8–15 mm long; lemmas more than 3/4 as long as the glumes; plants strongly rhizomatous ... Ammophila (in part)
33. Spikelets 1.2–7 mm long; lemmas less than 3/4 as long as the glumes; plants rhizomatous or not ... (34)
34. Sheaths closed for at least 1/2 their length ... (35)
34. Sheaths open for most of their length ... (36)
35. Calluses glabrous; exposed at maturity; lemmas 1–3-veined, unawned; [other genera may develop long caryopses when infected by nematodes or fungi; such caryopses are usually deformed and filled with eggs, larvae, or spores] ... Phippsia (in part)
35. Calluses with a ring of stiff hairs, hairs to about 1 mm long; lemmas 3–11-veined ... Dupontia (in part)
36. Spikelet bases usually U-shaped, sometimes cuneate; glumes equal, midveins usually strongly ciliate ... Phleum (in part)
36. Spikelet bases cuneate; glumes unequal, midveins not strongly ciliate ... (37)
37. Both glumes twice as long as the lemmas; lemmas pubescent ... Gastridium (in part)
37. Glumes from slightly shorter than to slightly longer than the lemmas; lemmas glabrous, sometimes scabridulous or scabrous ... (38)
38. Lemma awns 4–16 mm long; plants annual; paleas from 3/4 as long as to slightly longer than the lemmas ... Apera
38. Lemma awns to 10 mm, if longer than 4 mm, plants perennial and/or paleas less than 1/2 as long as the lemmas ... Agrostis (in part)
39. Caryopses usually as long as or longer than the lemmas, exposed at maturity; lemmas 1–3-veined, unawned; spikelets with 1 floret; sheaths of the flag leaves closed for at least 1/2 their length; calluses glabrous [other genera may develop long caryopses when infected by nematodes or fungi; such caryopses are usually deformed or filled with eggs, larvae, or spores] ... (40)
39. Caryopses shorter than the lemmas, concealed at maturity; lemmas 3–11-veined; spikelets with 1 or more florets; leaf sheaths open or closed; calluses glabrous or with hairs ... (41)
40. Lemmas 1-veined, narrowed to awnlike apices; sheaths strongly inflated; glumes absent; plants of temperate habitats ... Coleanthus
40. Lemmas 1–3-veined, apices acute to rounded; sheaths not inflated; glumes developed, caducous or persistent; plants of arctic or alpine habitats ... Phippsia (in part)
41. Panicle branches secund, appearing 1-sided; spikelets strongly imbricate, subsessile ... (42).
41. Panicle branches not secund; spikelets usually widely spaced to somewhat imbricate, usually clearly pedicellate, sometimes subsessile, sometimes on stipes ... (45)
42. Culms usually prostrate or procumbent; glumes obtuse to emarginate ... Sclerochloa (in part)
42. Culms erect or ascending; glumes apiculate to awn-tipped ... (43)
43. Lemmas awned, awns of the lowest lemmas 0.3–22 mm long ... Vulpia (in part)
43. Lemmas unawned, sometimes awn-tipped ... (44)
44. Spikelets circular to ovate or obovate in outline, with 1–2 florets; glumes almost entirely concealing the sides of the florets; disarticulation below the glumes ... Beckmannia
44. Spikelets oval in outline, longer than wide, with 2–6 florets; glumes partially exposing the sides of the florets; disarticulation above the glumes ... Dactylis
45. All or most spikelets in an inflorescence with 1 bisexual floret, sometimes with 1–2 sterile or staminate florets below the bisexual floret, the sterile florets sometimes resembling tufts of hair ... Poeae Subkey I
45. All or most spikelets in an inflorescence with 2–25 sexual florets, usually all florets bisexual or the distal florets sterile or unisexual, sometimes all florets unisexual, sometimes the plants unisexual ... Poeae Subkey II

POEAE SUBKEY I

Synoecious or monoecious grasses with panicles having at least some branches longer than 1 cm and spikelets with only 1 bisexual floret, sometimes with 1–2 sterile or staminate florets below the bisexual floret.

1. Spikelets with 1–2 staminate or sterile florets below the bisexual floret, sterile florets sometimes knoblike or resembling tufts of hair ... (2)
1. Spikelets without staminate or sterile florets below the bisexual florets ... (4)
2. Spikelets with 2 florets of similar size, the lower floret staminate; lower lemmas awned, the lemmas of the terminal floret unawned or awned ... Arrhenatherum
2. Spikelets with 2–3(4) florets, the lower 1–2 florets staminate or sterile, sometimes knoblike or resembling tufts of hair, sometimes larger than the bisexual floret; lemmas of the lower florets awned or unawned, the lemmas of the terminal floret unawned ... (3)
3. Lower sterile florets 2, from shorter than to exceeding the bisexual floret; fresh leaves sweet-smelling when crushed ... Anthoxanthum (in part)
3. Lower sterile florets 1–2, varying from knoblike projections on the callus of the bisexual floret to linear or lanceolate lemmas up to 3/4 as long as the bisexual floret; fresh leaves not sweet-smelling when crushed ... Phalaris (in part)
4. Spikelets 15–50 mm long; lemmas usually dorsally awned, awns 20–90 mm long, sometimes unawned ... Avena (in part)
4. Spikelets 1–15 mm long; lemmas unawned or awned, awns to 18 mm long, basal, dorsal, subterminal, or terminal ... (5)
5. Glume bases gibbous and subcoriaceous; disarticulation above the glumes ... Gastridium (in part)
5. Glumes bases not gibbous, usually membranous; disarticulation above or below the glumes ... (6)
6. Lemmas awned, awns longer than 2 mm ... (7)
6. Lemmas unawned or, if awned, awns shorter than 2 mm ... (15)
7. Glumes coriaceous, rigid, hispid or scabrous; lemmas awned, awns 5–14.5 mm long, subterminal ... Limnodea
7. Glumes membranous, flexible, glabrous or with soft hairs, usually smooth; lemmas awned, awns 0.5–18 mm long, sometimes subterminal ... (8)
8. Disarticulation below the glumes ... (9).
8. Disarticulation above the glumes ... (11)
9. Spikelets borne on stipes; disarticulation at the base of the stipes; lemmas 0.5–2 mm long; glumes usually awned, sometimes unawned ... Polypogon (in part)
9. Spikelets borne on pedicels; disarticulation immediately below the glumes; lemmas 1.5–7.5 mm long; glumes usually unawned ... (10)
10. Paleas absent or greatly reduced; lemma awns attached at midlength or below; glume bases often fused; rachillas not prolonged beyond the floret base ... Alopecurus (in part)
10. Paleas from 3/4 to nearly as long as the lemmas; lemma awns subterminal; glume bases not fused; rachillas usually prolonged beyond the base of the distal floret as a minute stub or slender bristle ... Cinna
11. Rachillas not prolonged beyond the base of the distal floret; paleas absent, minute, or subequal to the lemmas; lemmas 0.5–4 mm long ... (12)
11. Rachillas prolonged beyond the base of the distal floret; paleas at least 1/2 as long as the lemmas; lemmas 1–8 mm long ... (13)
12. Lemmas usually glabrous, sometimes pubescent, unawned or awned, if awned, the awns usually shorter than 4.5 mm, sometimes to 10 mm long, basal, dorsal, subterminal, or terminal; veins usually not excurrent, if excurrent, not forming awnlike teeth; panicles often open, sometimes contracted and cylindrical ... Agrostis (in part)
12. Lemmas pilose and dorsally awned, awns 4.5–6 mm long; lateral lemma veins excurrent, forming 4 teeth, teeth sometimes awnlike; panicles dense ... Bromidium (in part)
13.Plants annual; calluses glabrous or sparsely hairy; lemma apices entire; marginal veins not excurrent; awns subterminal ... Apera
13. Plants perennial; calluses usually abundantly, sometimes sparsely hairy, hairs 0.2–6.5 mm long; lemma apices denticulate or the marginal veins excurrent; awn attachment from nearly basal to subterminal ... (14)
14. Lemma surfaces mostly glabrous; lemma apices denticulate; marginal lemma veins not excurrent ... Calamagrostis (in part)
14. Lemma surfaces hairy; lemma apices erose or toothed; marginal lemma veins excurrent ... Lachnagrostis
15. Disarticulation below the glumes ... (16)
15. Disarticulation above the glumes ... (18)
16. Glumes attached to stipes, disarticulation at the base of the stipes; glumes usually awned, awns flexuous ... Polypogon (in part)
16. Glumes attached to pedicels, disarticulation immediately beneath the glumes; glumes unawned or with stiff awns ... (17)
17. Lemma awns subterminal; glume bases not fused; paleas from 3/4 to nearly as long as the lemmas; rachillas prolonged beyond the base of the distal floret for 0.1–1.3 mm ... Cinna
17. Lemma awns attached at midlength or below; glume bases often fused; paleas absent or greatly reduced; rachillas not prolonged beyond the base of the distal floret ... Alopecurus (in part)
18. Glumes 8–15 mm long; plants strongly rhizomatous ... Ammophila (in part)
18. Glumes 1–10 mm long; plants rhizomatous or not ... (19)
19. Spikelets dorsally compressed; lemmas dark, coriaceous, lustrous, and glabrous ... Milium
19. Spikelets laterally compressed, sometimes weakly so; lemmas not simultaneously dark, coriaceous, lustrous, and glabrous ... (20)
20. Lower glumes exceeded by the florets, upper glumes exceeded by to exceeding the florets; sheaths usually closed for up to 1/5 their length ... Arctagrostis
20. Both glumes subequal to or exceeding the florets; sheaths open to the base ... (21)
21. Paleas absent or minute to subequal to the lemmas, not veined; rachillas not prolonged beyond the base of the distal florets; lemmas often unawned, sometimes awned, awn attachment basal to terminal ... Agrostis (in part)
21. Paleas more than 1/2 as long as the lemmas, 2-veined; rachillas prolonged beyond the base of the floret by at least 0.1 mm; lemmas often awned, awn attachment usually on the proximal 1/2 of the lemma ... (22)
22. Calluses hairy, hairs 0.5–4.5 mm long; lemmas usually awned, awns usually attached to the proximal 1/2, if the attachment higher, the callus hairs longer than 2 mm and/or the awns geniculate ... Calamagrostis (in part)
22. Calluses glabrous or with hairs to about 1 mm long; lemmas unawned or terminally awned, awns to 1(2.2) mm long ... (23)
23. Glumes 4–9 mm long; sheaths closed for 1/2–2/3 their length; plants of arctic and subarctic regions ... Dupontia (in part)
23. Glumes 1.6–4.3 mm long; sheaths open; plants of western North America, from Alaska to California ... Podagrostis

POEAE SUBKEY II

Synoecious, monoecious, or dioecious grasses with spikelets having 2–22 sexual florets, the lower florets sexual, the distal florets sometimes sterile.

1. One or both glumes exceeding the adjacent lemmas, sometimes exceeding the distal floret ... (2)
1. Both glumes shorter than or subequal to the adjacent lemmas ... (24)
2. All lemmas within a spikelet unawned or with awns shorter than 2 mm ... (3)
2. One or all lemmas within a spikelet awned, the awns at least 2 mm long ... (13)
3. Spikelets usually with 2 florets, lemmas of the lower florets unawned, lemmas of the upper florets awned, the awns strongly curved or hooked ... Holcus (in part)
3. Spikelets with 2–22 florets, all lemmas unawned or if awned, the awns straight ... (4).
4. Leaf sheaths closed for at least 1/2 their length; caryopses falling free of the lemma and palea; plants of arctic or subarctic regions ... (5)
4. Leaf sheaths open for most of their length; caryopses usually falling with the lemma and palea attached; plants of temperate, arctic, or subarctic regions ... (6)
5. Lemma apices obtuse; paleas subequal to the lemmas ... Arctophila (in part)
5. Lemma apices acute to acuminate; paleas shorter than the lemmas ... Dupontia (in part)
6. Glumes 15–50 mm long; plants annual ... Avena (in part)
6. Glumes 0.4–9 mm long; plants annual or perennia ... (7)
7. Lemmas inflated, about as wide as long, with broadly rounded backs; calluses glabrous; spikelets pendulous ... Briza (in part)
7. Lemmas not inflated, longer than wide, keeled to rounded over the midvein; calluses usually with hairs, sometimes glabrous; spikelets not pendulous ... (8)
8. Plants annual; spikelets with 2 florets; lemmas evenly hairy, 3-veined ... Dissanthelium
8. Plants usually perennial, sometimes annual; spikelets with 2–10 florets; lemmas usually glabrous or with unevenly distributed hairs, never both annual and with evenly distributed hairs, 3–9-veined ... (9)
9. Rachilla internodes hairy, hairs at least 1 mm long ... (10)
9. Rachilla internodes glabrous or with hairs shorter than 1 mm on the distal portion ... (11)
10. Lemma apices truncate, erose to 2–4-toothed ... Deschampsia (in part)
10. Lemmas apices acute, bifid ... Trisetum (in part)
11. Plants strongly rhizomatous; glumes 5–9 mm long ... Scolochloa (in part)
11. Plants not or weakly rhizomatous; glumes 0.4–9 mm long ... (13)
12. Panicle branches densely pubescent, hairs 0.1–0.2 mm long; lemma apices entire, sometimes mucronate; lemma veins converging distally ... Koeleria (in part)
12. Panicles branches glabrous, sometimes scabrous; lemma apices entire or serrate to erose, not mucronate; lemma veins more or less parallel distally ... Puccinellia (in part)
13. Lemmas 14–40 mm long; glumes 7–11-veined ... Avena
13. Lemmas 1.3–16 mm long; glumes 1–9-veined ... (14)
14. Lemmas 7–16 mm long ... (15)
14. Lemmas 1.3–7 mm long ... (16)
15. Adaxial surfaces of the leaves ribbed; rachillas pilose on all sides; ligules truncate to rounded, 0.5–1.5 mm long ... Helictotrichon (in part)
15. Adaxial surfaces of the leaves unribbed; rachillas glabrous on the side adjacent to the paleas, hairy elsewhere; ligules acute to truncate, 0.5–7 mm long ... Avenula (in part)
16. Lemmas 1-veined, awned, awns articulated near the middle, the proximal segment yellow-brown to dark brown, the distal segment pale green to whitish, the junction marked by a ring of minute, conical protuberances ... Corynephorus
16. Lemmas 3–7-veined, at least some lemmas awned, awns not articulated ... (17)
17. Disarticulation below the glumes ... (18)
17. Disarticulation above the glumes ... (19)
18. Spikelets usually with 2 florets, the lower florets bisexual with unawned lemmas, the upper florets staminate or sterile with awned lemmas ... Holcus (in part)
18. Spikelets with 2–5 florets, all florets bisexual or sometimes the distal florets sterile; all lemmas awned ... Trisetum (in part)
19. Lowest lemma within a spikelet unawned or with a straight awn up to 4 mm long, the distal lemmas within a spikelet always awned, awns 10–16 mm long, geniculate ... Ventenata (in part)
19. All lemmas within a spikelet similarly awned or the awns of the lower lemmas longer than those of the upper lemmas, or the upper lemmas with awns shorter than 10 mm ... (20)
20. Callus hairs about 1/2 as long as the lemmas; rachillas not prolonged or prolonged about 0.5 mm or less beyond the base of the distal floret; plants loosely cespitose ... Vahlodea
20. Calluses usually glabrous or the hairs much shorter than 1/2 the length of the lemmas, if about 1/2 as long, the rachillas prolonged more than 0.5 mm beyond the base of the distal floret and the plants usually densely cespitose ... (21)
21. Plants annual; culms 1–60 cm tall; rachillas not prolonged beyond the base of the distal florets ... Aira (in part)
21. Plants perennial or annual; culms 5–150 cm tall; rachillas prolonged beyond the base of the distal florets, the prolongations hairy ... (22)
22. Rachilla internodes glabrous or with hairs shorter than 1 mm on the distal portion; panicle branches densely pubescent, not scabrous ... Koeleria (in part)
22. Rachilla internodes hairy, hairs at least 1 mm long; panicles branches usually glabrous, sometimes scabrous ... (23)
23. Lemma apices truncate, erose or 2–4-toothed ... Deschampsia (in part)
23. Lemmas apices acute, bifid ... Trisetum (in part)
24. Upper lemma(s) in a spikelet with hooked or geniculate awns, awns 2–16 mm long; lowest lemmas unawned or terminally awned, awns straight, to 4 mm long ... (25)
24. Lemmas all similarly awned or unawned ... (26)
25. Spikelets 9–15 mm long, with 2–20 florets; awns of the distal florets 10–16 mm long ... Ventenata (in part)
25. Spikelets 3–7 mm long, with 2 florets; awns of the distal floret 2–5 mm long ... Holcus (in part)
26. Lower lemmas with awns longer than 2 mm ... (27)
26. Lower lemmas unawned, mucronate, or with awns up to 2 mm long ... (32)
27. Calluses hairy; rachillas prolonged beyond the base of the distal florets ... (28)
27. Calluses glabrous or sparsely hairy; rachillas sometimes prolonged beyond the base of the distal floret ... (29)
28. Glumes shorter than the adjacent lemmas; ligules 4.5–20 mm long ... Amphibromus
28. Glumes subequal to the adjacents lemmas; ligules 0.5–6 mm long ... Trisetum (in part)
29. Panicles dense, spikelike; plants annual ... Rostraria (in part)
29. Panicles not both dense and spikelike; plants perennial or annual ... (30)
30. Anthers 1; plants annual ... Vulpia (in part)
30. Anthers 3; plants perennial ... (31)
31. Leaves without auricles; blades flat, conduplicate, involute, or convolute ... Festuca (in part)
31. Lower leaves with auricles; blades flat ... Schedonorus (in part)
32. Lemmas inflated, about as wide as long; spikelets pendulous ... Briza (in part)
32. Lemmas not inflated, longer than wide; spikelets appressed to divergent, not pendulous ... (33)
33. Lemmas apices rounded, truncate, obtuse, or emarginate ... (34)
33. Lemma apices acute to acuminate, sometimes mucronate or shortly awn-tipped ... (42)
34. Lemmas conspicuously 3-veined; lower glumes 0–3-veined ... (35)
34. Lemmas (3)5–9-veined, the veins often inconspicuous; lower glumes 1–5-veined ... (36)
35. Lower glumes without veins; lemmas not keeled over the lateral veins ... Catabrosa
35. Lower glumes 1–3-veined; lemmas keeled over each vein ... Cutandia (in part)
36. Inflorescences usually exceeded by the leaves; lemmas indurate at maturity; pedicels 0.5–0.8 mm thick; culms usually prostrate to procumbent, sometimes ascending; upper glumes 2.6–6.2 mm long ... Sclerochloa (in part)
36. Inflorescences exceeding the leaves at maturity; lemmas usually membranous at maturity, sometimes coriaceous; pedicels less than 0.5 mm thick; culms usually erect; upper glumes 0.7–4.5(9) mm long ... (37)
37. Lower glumes about as long as the upper glumes but no more than 1/2 as wide; disarticulation below the glumes ... Sphenopholis (in part)
37. Lower glumes shorter than the upper glumes or subequal and more than 1/2 as wide; disarticulation above the glumes ... (38)
38. Sheaths closed for more than 1/2 their length ... Arctophila (in part)
38. Sheaths open their entire length ... (39)
39. Panicle branches stiff; lemmas coriaceous; plants annual; culms to 60 cm tall ... Desmazeria (in part)
39. Panicle branches flexible; lemmas usually mem-branous, sometimes coriaceous; plants usually perennial, sometimes annual or biennial; culms 2–145 cm tall ... (40)
40. Lemma veins excurrent, lemma apices indistinctly 3-lobed or toothed; plants strongly rhizomatous, rhizomes succulent ... Scolochloa (in part)
40. Lemma veins not excurrent, lemma apices entire, serrate, or erose; plants sometimes rhizomatous, rhizomes not succulent ... 41
41. Lemma veins (5)7–9, prominent; plants of non-saline and non-alkaline habitats ... Torreyochloa (in part)
41. Lemma veins (3)5(7), inconspicuous or prominent; plants of saline and alkaline habitats ... Puccinellia (in part)
42. Lemmas (3)5–9-veined, veins more or less parallel distally, conspicuous ... (43)
42. Lemmas 3–9-veined, veins converging distally, usually inconspicuous, sometimes conspicuous ... (44)
43. Lemma veins (5)7–9; plants rhizomatous, growing in non-saline and non-alkaline habitats ... Torreyochloa (in part)
43. Lemma veins (3)5(7); plants not truly rhizomatous, sometimes the culms rooting at buried lower nodes, growing in saline and alkaline habitats ... Puccinellia (in part)
44. Lemmas conspicuously 3-veined, keeled over each vein; panicle branches divaricate; plants annual ... Cutandia (in part)
44. Lemmas inconspicuously (3)5–9-veined, sometimes keeled over the midvein, not over the other veins; panicle branches divaricate or not; plants annual or perennial ... (45)
45. Disarticulation below the glumes; lower glumes subequal to the upper glumes but no more than 1/2 as wide ... Sphenopholis (in part)
45. Disarticulation above the glumes, sometimes above the basal floret; lower glumes shorter than the upper glumes or, if subequal, more than 1/2 as wide ... (46)
46. Panicle branches smooth, hairy, hairs soft ... Koeleria (in part)
46. Panicle branches smooth or scabrous, glabrous or strigose, never covered with soft hairs ... (47)
47. Rachillas pilose, hairs at least 2 mm long (see Stipeae) ... Ampelodesmos
47. Rachillas glabrous or with hairs shorter than 1 mm ... (48)
48. Basal leaves with auricles ... Schedonorus (in part)
48. No leaves with auricles ... (49)
49. Lemma veins parallel distally; plants of saline and alkaline habitats ... Puccinellia (in part)
49. Lemma veins converging distally; plants of many habitats, including saline habitats ... (50)
50. Leaf blades with translucent lines on either side of the midvein, apices often prow-tipped; lemmas often with a tuft of hair at the base of the midvein; hila round to oval ... Poa (in part)
50. Leaf blades without translucent lines on either side of the midvein, apices not prow-tipped, often flat; lemmas without a tuft of hair below the midvein hila usually linear, always linear in perennial species ... (51)
51.Plants perennial ... (52)
51. Plants annual ... (53)
52. Plants and florets bisexual; glumes not translucent; caryopses obovoid-oblong ... Festuca (in part)
52. Plants unisexual; glumes translucent; caryopses fusiform ... Leucopoa
53. Ligules up to 1 mm long; lemma apices mucronate or awned ... Vulpia (in part)
53. Ligules 1–4 mm long; lemma apices never awned, sometimes mucronate ... (54)
54. Panicle branches up to 2 cm long, stiff, spikelet-bearing to the base; culms procumbent to erect ... Desmazeria (in part)
54. Panicles branches 2–10 cm long, flexible, spikelets confined to the distal portion; culms erect ... Eremopoa