Difference between revisions of "Poaceae tribe Poeae"

Revision as of 21:20, 16 December 2019

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.

Discussion

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., Catalan 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: xAgropogon (Agrostis x Polypogon, p. 668), xArctodupontia (Arctopbila x Dupontia, p. 604), xDupoa (Dupontia x Poa, p. 601), and ×Pucciphippsia (Puccinellia x Phippsia, p. 477). They are described on the pages indicated. In the key that follows, branch measurements include spikelets, but not awns.

Selected References

Catalan, P., E.A. Kellogg, and R.G. Olmstead. 1997. Phylogeny of Poaceae subfamily Pooideae based on chloroplast ndh¥ gene sequences. Molec. Phylogenet. Evol. 8:150-166

Catalan, P., P. Torrecilla, J.A. Lopez Rodriguez, and R.G. Olmsted. 2004. Phylogeny of the festucoid grasses of subtribe Loliinae and allies (Poeae, Pooideae) inferred from ITS and trnL-T sequences. Molec. Phylogenet. Evol. 31:517-541

Macfarlane, T.D. 1987. Poaceae subfamily Pooideae. 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., J.I. Davis, and J.J. Doyle. 1990. A phylogenetic analysis of chloroplast DNA restriction site variation in Poaceae subfam. Pooideae. PI. Syst. Evol. 172:83-97.

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.

Keys

1	All or almost all spikelets viviparous, the spikelets producing plantlets [if sexual spikelets are common, take the alternate lead].	> 2
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
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
3	Sheaths open; ligules 1.5-13 mm long	Deschampsia
1	Some, usually all, spikelets sexually functional, with 1-25 bisexual or unisexual florets, sometimes with sterile and sexual spikelets mixed within an inflorescence.	> 2
4	Inflorescences with 2 morphologically distinct forms of spikelets.	> 5
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
4	Inflorescences with all spikelets morphologically alike.	> 5
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
9	Spikelets with 1 functional floret, sometimes a reduced, sterile floret also present.	> 10
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
9	Spikelets with 2-25 functional florets.	> 10
13	Lemmas awned from about midlength, awns 8-26 mm long, twisted proximally.	> 14
14	Adaxial surfaces of the leaves ribbed; rachillas pilose on all sides; ligules truncate to rounded, 0.5-1.5 mm long	Helictotrichon
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
13	Lemmas unawned or apically awned, awns straight.	> 14
15	Spikelets sessile; lemmas 2-12 mm long.	> 16
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
15	Spikelets subsessile to pedicellate, pedicels 0.5-3 mm long.	> 16
17	Plants perennial	Festuca
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
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
8	Inflorescences panicles or racemes, with more than 1 spikelet associated with each node.	> 9
19	Inflorescences racemes or spikelike panicles, with all branches shorter than 1 cm [for opposite lead, see p. 382].	> 20
20	Leaves usually exceeding the inflorescences; culms usually prostrate to procumbent; lemmas indurate at maturity	Sclerochloa
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
22	Spikelets weakly laterally compressed, with stipes that fall with the spikelets; glume bases not fused; glumes usually awned	Polypogon
22	Spikelets strongly laterally compressed, without stipes; glume bases sometimes fused; glumes unawned or awned. 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
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
21	Spikelets disarticulating above the glumes; glume bases not fused.	> 22
24	Spikelets with 2-25 bisexual florets, the sterile or staminate florets, if present, distal to the bisexual florets.	> 25
25	Sheaths closed for at least 1/2 their length.	> 26
26	Lemma midveins sometimes excurrent up to 2.2 mm, other veins not excurrent; plants native, arctic	Dupontia
26	Lemmas with 3-5 veins excurrent, forming awnlike teeth; plants cultivated	Sesleria
25	Sheaths open for all or almost all of their length.	> 26
27	Distal lemmas, sometimes all lemmas, awned from below midlength	Aira
27	All lemmas unawned or apically awned.	> 28
28	Lemmas coriaceous at maturity, unawned, sometimes mucronate	Desmazeria
28	Lemmas membranous, apically awned, awns 0.3-22 mm long.	> 29
29	Lemma margins involute, not scarious	Vulpia
29	Lemma margins flat, scarious	Rostraria
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.	> 25
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
31	Fresh leaves not sweet-smelling when crushed; sterile lemmas unawned; bisexual lemmas usually hairy, sometimes sparsely so; glumes subequal, sometimes winged distally	Phalaris
31	Fresh leaves sweet-smelling when crushed; sterile lemmas awned; bisexual lemmas glabrous; glumes unequal, not winged	Anthoxanthum
30	Spikelets without sterile or staminate florets below the bisexual floret; glumes not winged distally.	> 31
32	Lemmas dorsally awned, awns geniculate; lateral lemma veins excurrent, forming 4 teeth, teeth sometimes awnlike	Bromidium
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
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
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
35	Calluses with a ring of stiff hairs, hairs to about 1 mm long; lemmas 3-11-veined	Dupontia
34	Sheaths open for most of their length.	> 35
36	Spikelet bases usually U-shaped, sometimes cuneate; glumes equal, midveins usually strongly ciliate	Phleum
36	Spikelet bases cuneate; glumes unequal, midveins not strongly ciliate.	> 37
37	Both glumes twice as long as the lemmas; lemmas pubescent	Gastridium
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
19	Inflorescences panicles, dense to open, sometimes compact, usually at least some branches longer than 1 cm [for opposite lead, see p. 380].	> 20
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
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	Phippsia
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.	> 40
41	Panicle branches secund, appearing 1-sided; spikelets strongly imbricate, subsessile.	> 42
42	Culms usually prostrate or procumbent; glumes obtuse to emarginate	Sclerochloa
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
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
41	Panicle branches not secund; spikelets usually widely spaced to somewhat imbricate, usually clearly pedicellate, sometimes subsessile, sometimes on stipes.	> 42
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	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	Subkey II

POEAE SUBKEY I

1	Spikelets with 1-2 staminate or sterile florets below the bisexual floret, sterile florets sometimes knoblike or resembling tufts of hair.	> 2
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
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
1	Spikelets without staminate or sterile florets below the bisexual florets.	> 2
4	Spikelets 15-50 mm long; lemmas usually dorsally awned, awns 20-90 mm long, sometimes unawned	Avena
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
5	Glumes bases not gibbous, usually membranous; disarticulation above or below the glumes.	> 6
6	Lemmas awned, awns longer than 2 mm.	> 7
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
9	Spikelets borne on stipes; disarticulation at the base of the stipes; lemmas 0.5-2 mm long; glumes usually awned, sometimes unawned	Polypogon
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
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
8	Disarticulation above the glumes.	> 9
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
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
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
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.	> 12
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
14	Lemma surfaces hairy; lemma apices erose or toothed; marginal lemma veins excurrent	Lachnagrostis
6	Lemmas unawned or, if awned, awns shorter than 2 mm.	> 7
15	Disarticulation below the glumes.	> 16
16	Glumes attached to stipes, disarticulation at the base of the stipes; glumes usually awned, awns flexuous	Polypogon
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
15	Disarticulation above the glumes.	> 16
18	Glumes 8-15 mm long; plants strongly rhizomatous	Ammophila
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
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 lemmas.	> 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
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
23	Glumes 1.6-4.3 mm long; sheaths open; plants of western North America, from Alaska to California	Podagrostis

POEAE SUBKEY II

1	One or both glumes exceeding the adjacent lemmas, sometimes exceeding the distal floret.	> 2
2	All lemmas within a spikelet unawned or with awns shorter than 2 mm.	> 3
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
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
5	Lemma apices obtuse; paleas subequal to the lemmas	Arctophila
5	Lemma apices acute to acuminate; paleas shorter than the lemmas	Dupontia
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.	> 5
6	Glumes 15-50 mm long; plants annual	Avena
6	Glumes 0.4-9 mm long; plants annual or perennial.	> 7
7	Lemmas inflated, about as wide as long, with broadly rounded backs; calluses glabrous; spikelets pendulous	Briza
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
10	Lemma apices truncate, erose to 2-4-toothed	Deschampsia
10	Lemmas apices acute, bifid	Trisetum
9	Rachilla internodes glabrous or with hairs shorter than 1 mm on the distal portion.	> 10
11	Plants strongly rhizomatous; glumes 5-9 mm long	Scolochloa
11	Plants not or weakly rhizomatous; glumes 0.4-9 mm long.	> 12
12	Panicle branches densely pubescent, hairs 0.1-0.2 mm long; lemma apices entire, sometimes mucronate; lemma veins converging distally	Koeleria
12	Panicles branches glabrous, sometimes scabrous; lemma apices entire or serrate to erose, not mucronate; lemma veins more or less parallel distally	Puccinellia
2	One or all lemmas within a spikelet awned, the awns at least 2 mm long.	> 3
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
15	Adaxial surfaces of the leaves ribbed; rachillas pilose on all sides; ligules truncate to rounded, 0.5-1.5 mm long	Helictotrichon
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
14	Lemmas 1.3-7 mm long.	> 15
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
18	Spikelets usually with 2 florets, the lower florets bisexual with unawned lemmas, the upper florets staminate or sterile with awned lemmas	Holcus
18	Spikelets with 2-5 florets, all florets bisexual or sometimes the distal florets sterile; all lemmas awned	Trisetum
17	Disarticulation above the glumes.	> 18
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
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
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
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
23	Lemmas apices acute, bifid	Trisetum
1	Both glumes shorter than or subequal to the adjacent lemmas.	> 2
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
25	Spikelets 9-15 mm long, with 2-20 florets; awns of the distal florets 10-16 mm long	Ventenata
25	Spikelets 3-7 mm long, with 2 florets; awns of the distal floret 2-5 mm long	Holcus
24	Lemmas all similarly awned or unawned.	> 25
26	Lower lemmas with awns longer than 2 mm.	> 27
27	Calluses hairy; rachillas prolonged beyond the base of the distal florets.	> 28
28	Glumes shorter than the adjacent lemmas; ligules 4.5-20 mm long	Amphibromus
28	Glumes subequal to the adjacent lemmas; ligules 0.5-6 mm long	Trisetum
27	Calluses glabrous or sparsely hairy; rachillas sometimes prolonged beyond the base of the distal florets.	> 28
29	Panicles dense, spikelike; plants annual	Rostraria
29	Panicles not both dense and spikelike; plants perennial or annual.	> 30
30	Anthers 1; plants annual	Vulpia
30	Anthers 3; plants perennial.	> 31
31	Leaves without auricles; blades flat, conduplicate, involute, or convolute	Festuca
31	Lower leaves with auricles; blades flat	Schedonorus
26	Lower lemmas unawned, mucronate, or with awns up to 2 mm long.	> 27
32	Lemmas inflated, about as wide as long; spikelets pendulous	Briza
32	Lemmas not inflated, longer than wide; spikelets appressed to divergent, not pendulous.	> 33
33	Lemmas apices rounded, truncate, obtuse, or emarginate.	> 34
34	Lemmas conspicuously 3-veined; lower glumes 0-3-veined.	> 35
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
34	Lemmas (3)5-9-veined, the veins often inconspicuous; lower glumes 1-5-veined.	> 35
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
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
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
38	Sheaths open their entire length.	> 39
39	Panicle branches stiff; lemmas coriaceous; plants annual; culms to 60 cm tall	Desmazeria
39	Panicle branches flexible; lemmas usually membranous, 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
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
41	Lemma veins (3)5(7), inconspicuous or prominent; plants of saline and alkaline habitats	Puccinellia
33	Lemma apices acute to acuminate, sometimes mucronate or shortly awn-tipped.	> 34
42	Lemmas (3)5-9-veined, veins more or less parallel distally, conspicuous.	> 43
43	Lemma veins (5)7-9; plants rhizomatous, growing in non-saline and non-alkaline habitats	Torreyochloa
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
42	Lemmas 3-9-veined, veins converging distally, usually inconspicuous, sometimes conspicuous.	> 43
44	Lemmas conspicuously 3-veined, keeled over each vein; panicle branches divaricate; plants annual	Cutandia
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
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
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, p. 110)	Ampelodesmos
47	Rachillas glabrous or with hairs shorter than 1 mm.	> 48
48	Basal leaves with auricles	Schedonorus
48	No leaves with auricles.	> 49
49	Lemma veins parallel distally; plants of saline and alkaline habitats	Puccinellia
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
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
52	Plants and florets bisexual; glumes not translucent; caryopses obovoid-oblong	Festuca
52	Plants unisexual; glumes translucent; caryopses fusiform	Leucopoa
51	Plants annual.	> 52
53	Ligules up to 1 mm long; lemma apices mucronate or awned	Vulpia
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
54	Panicles branches 2-10 cm long, flexible, spikelets confined to the distal portion; culms erect	Eremopoa