Poaceae
Poaceae tribe Andropogoneae
grass family
annual or perennial, herbaceous or woody, usually erect or ascending, sometimes prostrate or decumbent for much of their length, occasionally climbing, rarely floating;
nodes prominent, sometimes concealed by the leaf sheaths;
internodes hollow or solid, bases meristematic; branching from the basal nodes only or from the basal, middle, and upper nodes;
basal branching extravaginal or intravaginal; branching from the upper nodes intravaginal, extravaginal, or infravaginal.
7-600 cm, annual, not woody, often reddish or purple, particularly at the nodes, often branched above the base.
open;
ligules usually scarious to membranous, ciliate or not;
blades mostly well-developed, leaves subtending an inflorescence or an inflorescence unit often with reduced blades.
alternate, 2-ranked, each composed of a sheath and blade encircling the culm or branch;
sheaths usually open, sometimes closed, the margins fused for all or part of their length;
auricles (lobes of tissue extending beyond the margins of the sheaths on either side) sometimes present;
ligules usually present at the sheath-blade junction, particularly on the adaxial surface, abaxial ligules common in the Bambusoideae, membranous, sometimes ciliate, adaxial ligules usually present, of membranous to hyaline tissue, a line of hairs, or a ciliate membrane;
blades usually linear to lanceolate, occasionally ovate to triangular, bases sometimes pseudopetiolate (having a petiole-like constriction), venation usually parallel, sometimes with evident cross veins, occasionally divergent.
(synflorescences) usually compound, composed of simple or complex aggregations of primary inflorescences, aggregations paniculate, spicate, or racemose or of spikelike branches, often with an evident rachis (central axis), primary inflorescences spikelets, pseudospikelets, or spikelet equivalents;
inflorescence branches usually without obvious bracts.
terminal, frequently on both the culms and their branches, sometimes also axillary, usually of 1-many spikelike branches, these in digitate clusters of 1-13+ on a peduncle or attached, directly or indirectly, to elongate rachises, often partially to almost completely enclosed by the subtending leaf sheath at maturity, in some taxa axillary inflorescences composed of multiple-stalked pedunculate clusters of inflorescence branches subtended by a modified leaf;
disarticulation usually in the branch axes beneath the sessile florets, the dispersal unit being a sessile floret, the internode to the next sessile floret, the pedicel, and the pedicellate spikelet (branches with disarticulating axes are termed rames in the following accounts), sometimes beneath the glumes, the branch axes remaining intact.
with (0-1)2(3-6) glumes (empty bracts) subtending 1-60 florets, glumes and florets distichously attached to a rachilla (central axis);
pseudospikelets with bud-subtending bracts below the glumes.
pairs or triplets komogamous (spikelets in the unit sexually alike) or beterogamous (spikelets in the unit sexually dissimilar);
spikelets of unequally pedicellate pairs usually homogamous and homomorphic;
spikelets in sessile-pedicellate pairs or triplets usually heterogamous and heteromorphic;
sessile spikelets usually bisexual;
pedicellate spikelets usually smaller than the sessile spikelets, often staminate or sterile, sometimes absent.
usually with an odd number of veins, sometimes awned.
exceeding and usually concealing the florets (excluding the awns), rounded or dorsally compressed, usually tougher than the lemmas;
lower florets in bisexual or pistillate spikelets sterile or staminate, often reduced to a hyaline scale;
upper florets bisexual or pistillate, lemmas often hyaline, sometimes with an awn that exceeds the glumes;
lodicules cuneate;
anthers usually 3.
free or fused to the rachis internodes.
bisexual, staminate, or pistillate, usually composed of a lemma (lower bract) and palea (upper bract), lodicules, and reproductive organs, often laterally or dorsally compressed, sometimes round in cross section;
lemmas usually with an odd number of veins, often awned, bases frequently thick and hard, forming a callus, backs rounded or keeled over the midvein, awns usually 1(-3), arising basally to terminally;
paleas usually with 2 major veins, with 0 to many additional veins between the major veins, sometimes also in the margins, often keeled over the major veins;
lodicules (0)2-3, inconspicuous, usually without veins, bases swelling at anthesis;
stamens usually 3, sometimes 1(2) or 6+, filaments capillary, anthers versatile, usually all alike within a floret, sometimes 1 or 2 evidently longer than the others;
ovaries 1-loculed, with (1)2-3(4) styles or style branches, stigmatic region usually plumose.
caryopses, pericarp usually dry and adhering to the seed, sometimes fleshy or dry and separating from the seed at maturity or when moistened;
embryos ⅕ as long as to almost equaling the caryopses, highly differentiated with a scutellum (absorptive organ), a shoot with leaf primordium covered by the coleoptile (shoot sheath), and a root covered by the coleorhiza (root sheath);
hila punctate to linear.
pathway NADP-ME;
bundle sheaths single.
spikelets variable, sometimes similar to the sessile spikelets, sometimes differing in sexuality and shape, sometimes missing.
= 5,6, 7, 9, 10, 11, 12.
= usually 9 or 10, or possibly 5 with 9 and 10 reflecting ancient polyploidy.
Poaceae
Poaceae tribe Andropogoneae
The Poaceae or grass family includes approximately 700 genera and 11,000 species (Chen et al. 2006). The two grass volumes in this series treat 10 subfamilies, 25 tribes, 236 genera, and 1373 species. Of these, all the subfamilies, 22 tribes, 136 genera, and 892 species are native to the Flora region; 2 tribes, 78 genera, and 290 species have become established in the region. The remaining taxa include ornamental species; species grown for research purposes; species that, if introduced to the region, would pose a threat to important agricultural species; and a few waifs, i.e., species that have been found in the region but have not become established. Most of the waifs are species that were found on ballast dumps near ports around the turn of the last century.
Grasses constitute the fourth largest plant family in terms of number of species. Nevertheless, the family is clearly more significant than any other plant family in terms of geographic, ecological, and economic importance. Grasses grow in almost all terrestrial environments, including dense forests, open deserts, and freshwater streams and lakes. There are no truly marine grasses, but some species grow within reach of the highest tides.
In addition to being widely distributed, grasses are often dominant or co-dominant over large areas. The importance of such areas to humans is reflected in the many words that exist for grasslands, words such as meadow, palouse, pampas, prairie, savanna(h), steppe, and veldt. Not surprisingly, given their abundance and prevalence, grasses are of great ecological importance as soil stabilizers and as providers of shelter and food for many different animals.
The economic importance of grasses to humans is almost impossible to overestimate. The wealth of individuals and countries is dependent on the availability of such sources of grain as Triticum (wheat), Oryza (rice), Zea (corn or maize), Hordeum (barley), Avena (oats), Secale (rye), Eragrostis (tef), and Zizania (wild rice). Most countries invest heavily in research programs designed to develop better strains of these grasses and the many other grasses that are used for livestock, soil stabilization, and revegetation. Developing improved grasses for recreation areas, such as playing fields, golf courses, and parks, is also a major industry in many parts of the world; increasing recognition of the aesthetic value af grasses is reflected in their prominence in horticultural catalogs.
There are, of course, grasses that are considered undesirable, at least in some parts of the world, but even the most obnoxious grasses may be well-regarded over a portion of their range. For instance, Bromus tectorum (cheatgrass) is a noxious, fire-prone invader of western North American ecosystems; it is also welcomed as a source of early spring feed in some parts of the Flora region. Cynodon dactylon (bermudagrass) is listed as a noxious weed in some jurisdictions; in others it is valued as a lawn grass.
Although grasses are widespread and often dominant in open areas, all evidence points to an origin of the family in forests, most likely in the Southern Hemisphere, at least 55-70 mya (Grass Phylogeny Working Group 2001). Recent evidence from phytoliths (isolated silica bodies commonly produced inside the epidermal cells of grasses and some other plants) embedded in fossil coprolites strongly suggests that grasses evolved earlier in the Cretaceous than previously thought (Prasad et al. 2005). Living representatives of the three earliest lineages of the grass family, together comprising about 30 species, are perennial, broad-leaved plants of relatively small stature, native to tropical or subtropical forests in South America, Africa, southeast Asia, some Pacific Islands, and northern Australia. The major diversification of the family probably occurred in the mid-Cenozoic, and was associated with climatic changes that produced more open habitats. All major lineages of the grass family were present by the middle of the Miocene (Jacobs et al. 1999), and C4 photosynthesis in grasses had evolved by then, as well.
Molecular and morphological data unequivocally support a single origin for the Poaceae (Grass Phylogeny Working Group 2001). The caryopsis, a single-seeded, usually dry and indehiscent fruit with the pericarp usually strongly adherent to the seed, and the laterally positioned, highly differentiated embryo are unique to grasses. Beyond the three early-diverging lineages (Anomochlooideae Potztal, Pharoideae, and Puelioideae L.G. Clark et al.), the great diversity of grasses can be divided into two major lineages: the BEP clade (Bambusoideae, Ehrhartoideae, and Pooideae); and the PACMCAD clade (Panicoideae, Arundinoideae, Chloridoideae, Micrairoideae Pilger, Centothecoideae, Aristidoideae, and Danthonioideae, i.e., the PACCAD clade of volume 25 plus the Micrairoideae, support for recognition of which was obtained after publication of that volume). Relationships among the BEP grass lineages remain uncertain, and some evidence points to the Pooideae as being more closely related to the PACMCAD clade than to the Bambusoideae or Ehrhartoideae. The PACMCAD clade includes all known C4 or warm-season grasses.
The closest relatives of the Poaceae lie within a group of six families, all native primarily to the Southern Hemisphere: Joinvilleaceae Toml. & A.C. Sm., Ecdeiocoleaceae D.F. Cutler &c& Airy Shaw, Restionaceae R. Br., Centrolepidaceae Endl., Anarthriaceae D.E Cutler &c& Airy Shaw, and Flagellariaceae Dumort. (Poales Small, sensu stricto). Joinvilleaceae, Ecdeiocoleaceae, and Poaceae constitute a three family clade, with Ecdeiocoleaceae probably being closer than Joinvilleaceae to the Poaceae (Bremer 2000; Bremer 2002; Michelangeli et al. 2003). Rudall et al. (2005), based on a study of reproductive structures in the Ecdeiocoleaceae, suggest that the grass caryopsis may represent "one end of a transformation series embodied by the reduced gynoecial structure and indehiscent fruit of other Poales such as Flagellaria and Ecdeiocolea" (p. 1441).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
The tribe Andropogoneae includes about 87 genera and 1060 species, of which 31 genera and 102 species have been found in the Flora region; some of these have not become established. The tribe is common in tropical and subtropical regions, particularly in areas with significant summer rains, such as the central plains of North America. Two of the grasses that used to dominate the prairies of central North America, Andropogon gerardii and Schizachyrium scoparium (Big and Little Bluestem, respectively), are member of the Andropogoneae. The reddish-purplish coloration that characterizes the culms and leaves of many Andropogoneae gives a striking aspect to grasslands (and lawns) dominated by its members.
Members of the Andropogoneae differ from those of Paniceae in the reduced lemmas and paleas of their florets and, usually, in their paired, unequally pedicellate spikelets, disarticulating inflorescence branches (rames), and the manner in which these branches are aggregated into inflorescences. Unequally pedicellate spikelet pairs are found in many other tribes, but they are more common, and the pedicels more strikingly unequal in length, in the Andropogoneae. Recent molecular work supports recognition of the tribe with one modification of its traditional limits, the incorporation of Arundinella and Tristachya (Kellogg 2000). There is less agreement on the tribe's internal structure and its relationship to the Paniceae (Clayton and Renvoize 1986; Kellogg 2000; Spangler 2000; Guissani et al. 2001).
Inflorescence Structures Describing inflorescence structures in the Andropogoneae is not simple. There is a basic pattern, but its many modifications have resulted in great structural diversity. The following paragraphs provide an overview of this diversity and explain the words and phrases used in describing it. Diagrammatic representations of many of the structures mentioned are presented on pages 604 and 605.
Spikelets Members of the Andropogoneae, like those of the Paniceae, generally have two florets per spikelet, the lower floret usually being reduced in size and sterile or staminate, and the upper floret bisexual (p. 604). Despite this similarity, spikelets of the two tribes are easy to distinguish. In the Paniceae, the lowest glume is usually much shorter than the floret, and the upper florets usually have lemmas that are thicker and tougher than the glumes and lower lemmas. In the Andropogoneae, the glumes usually exceed and enclose both florets, and are thicker and tougher than the lemmas. The florets of the Andropogoneae contrast strongly with the glumes, having hyaline or thinly membranous lemma bodies and hyaline paleas, or, in many cases, no palea. They are almost always completely concealed by the glumes, except that the upper floret often has an awn that projects beyond the glumes.
In some Andropogoneae, the glumes are merely thickly membranous, but most genera have coriaceous or indurate glumes. The lower glumes are sometimes tougher and larger than the upper glumes, and may even conceal the upper glumes as, for example, in Heteropogon (p. 681). In such genera, the lower glumes may be mistaken for lemmas. In dioecious species, or monoecious species with strongly differentiated staminate and pistillate spikelets, the staminate spikelets usually have softer glumes than the pistillate spikelets.
Spikelet Units The basic element of the inflorescence structure in the Andropogoneae is the spikelet unit. These units usually consist of pairs of spikelets, one sessile and one pedicellate (e.g., Saccharum bengalense, p. 615), but they may consist of a pair of unequally pedicellate spikelets (e.g., Miscanthus sacchariflorus, p. 619) or of three spikelets (e.g., Chysopogon fulvus, p. 635). If there are three spikelets in the unit, one is usually sessile and the other two pedicellate, but a few genera, such as Polytrias, have two sessile spikelets and one pedicellate spikelet.
Unequally pedicellate spikelet pairs or triplets are found in other tribes, but in the Andropogoneae they usually differ in size, shape, and sexuality. Spikelet units with spikelets that differ in their sexuality are described as heterogamous; those with sexually similar spikelets are said to be homogamous. Spikelet units with morphologically dissimilar spikelets are beteromorphic (e.g., Andropogon longiberbis, p. 663); those with morphologically similar spikelets are homomorphic (e.g., Chrysopogon zizanioides, p. 636). In most Andropogoneae, the spikelet units are heterogamous and heteromorphic. The sessile spikelets usually contain a bisexual or pistillate floret, and often exhibit features such as awns and calluses that are related to seed dispersal and establishment (Peart 1984); the pedicellate spikelets are usually staminate, sterile, vestigial, or even absent. In some genera the situation is reversed, the pedicellate spikelets being bisexual or pistillate, and the sessile spikelets staminate or sterile. Sterile and staminate spikelets are sometimes morphologically similar to the pistiallye or bisexual spikelets, but usually lack the features associated with seed dispersal and establishment. A few genera have no staminate or sterile spikelets, merely empty pedicels associated dwith the bisexual sessile spikelets, as in Sorghastrum (p. 632) or even, as in Arthraxon (p. 679), with only a stump where the pedicel and its spikelet would be. Inflorescence Structure Further complexity is introduced to the Andropogoneae inflorescence structure by the manner in which the spikelet units are aggregated and the mode of disarticulation. Three patterns can be identified. The simplest pattern consists of inflorescences similar to those common in other tribes, in which neither the rachis nor the inflorescence branches break up at maturity. Genera with such inflorescences [e.g., Miscanthus (p. 619) and Imperata (p.622)] have unewually pedicellate spikelets, and disarticulation is below the glumes. Such inflorescences are, however, in the minority within the Andropogoneae. A more common situation is for the spikelets to be in sessile-pedicellate pairs and disarticulation to be in the branch axes, immediately below the attachment of the sessile spikelets. The resulting dispersal unit consists of the spikelet pair plus the internode that extends from the sessile spikelet to the next most distal sessile spikelet. These disarticulating inflorescence branches, termed rames in this Flora, form the basic unit of the typical Andropogoneae inflorescence. In other publications, the rames are often called racemes, a word that is restricted in this Flora to an entire inflorescence, not just an inflorescence branch. Rames are usually composed of several spikelet units, but sometimes of only one. The spikelets may be evenly distributed, or the base of the rame axis may be naked. Individual plants may bear few to many rames, and the rames themselves may be aggregated in a wide array of primary and secondary arrangements; they may also be branched.
One or more rames may be borne on a single stalk. If this stalk is attached to a rachis, the unit formed by the stalk and its rame(s) constitutes an inflorescence branch. Such a pattern is seen, for example, in Sorghum halepense (p. 629) and Bothriochloa bladhii (p. 647). A more common sit-uation is for one or more rames to be attached digitately to a common stalk, the peduncle. This peduncle may terminate a culm (as in Dichanthium annulatum [p. 638] or Elionurus [p. 686]) or be axillary to a subtending leaf (as in Andropogon hallii [p. 654] and Hemarthria altissima [p. 686]). Each peduncle and its associated rame(s) constitutes an inflorescence unit.
False panicles represent a further level of complexity. In these, the inflorescence units terminate rays, each of which has a prophyll, a 2-veined structure, in its axil. Several rays may develop within the axil of a single leaf sheath, and rays may themselves give rise to subtending leaves with multiple rays in their axils. The result is a complex, tiered inflorescence in which only the ultimate units are easily described. Such inflorescences are found, for example, in Andropogon glomeratus (p. 663) and Cymbopogon citratus (p. 667). Fortunately, identification of the Andropogoneae does not require analyzing false panicles, merely their ultimate inflorescence units.
In another inflorescence pattern, the rame axes are thick and the pedicels are either closely appressed or even fused to the rame axes. In these genera, the pedicellate spikelets are often highly reduced or absent. Pistillate rames of Tripsacum (p. 697) and wild taxa of Zea (p. 700) represent an extreme example of this pattern. In these genera, the sessile spikelets are completely embedded in the rame axes, the lower glumes being indurate and completely concealing the florets. Less extreme examples are seen in Coelorachis (p. 689) and Hackelochloa (p. 694).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key to Tribes
1. Leaf blades with divergent veins; spikelets unisexual and dimorphic, the pistillate lemmas with uncinate hairs (Pharoideae; FNA 24:11) | Phareae |
1. Leaf blades with parallel veins; spikelets bisexual, unisexual, or modified into plantlets, the pistillate lemmas never with uncinate hairs. | → 2 |
2. Culms perennial, woody or herbaceous, often developing complex branching systems from the upper nodes; leaves on the upper portion of the culms, or distal on the branches, usually pseudopetiolate (Bambusoideae). | → 3 |
3. Culms woody, to 30 m tall; leaves strongly dimorphic, those of the main culms (culm leaves) with expanded sheaths and often with reduced, non-photosynthetic blades, those of the branches (foliage leaves) with abaxial ligules; blades of the distal leaves not folding at night or under stress; florets bisexual; plants native or introduced, often cultivated (FNA 24:15) | Bambuseae |
3. Culms herbaceous, to 3.5 m tall or climbing; leaves not strongly dimorphic; blades of the distal leaves often folding at night or under stress; florets unisexual; plants known only in cultivation in the Flora region (FNA 24:29) | Olyreae |
2. Culms usually annual, sometimes facultatively perennial, rarely woody, sometimes branching from the upper nodes but the branching system not complex; leaves usually not pseudopetiolate. | → 4 |
4. Spikelets almost always with 2 florets, the lower florets in the spikelets always sterile or staminate, frequently reduced to lemmas, occasionally missing, the upper florets bisexual, staminate, or sterile, unawned or awned from the lemma apices or, if the lemmas bilobed, from the sinuses; glumes membranous and the upper lemma stiffer than the lower lemma, or both florets reduced and concealed by the stiff to coriaceous glumes; rachilla not prolonged beyond the second floret (Panicoideae, in part). | → 5 |
5. Glumes flexible, membranous, the lower glumes usually shorter than the upper glumes, sometimes missing, the upper glumes usually subequal to or exceeded by the upper floret; lower lemmas membranous; upper lemmas usually coriaceous to indurate, sometimes membranous; upper paleas similar in texture; spikelets usually single or in pairs, occasionally in triplets and all pedicellate, often shortly so) (FNA 25:353) | Paniceae |
5. Glumes stiff, coriaceous to indurate, often subequal, at least 1 and usually both exceeding the upper floret (excluding the awn); both lemmas hyaline; paleas hyaline or absent; most spikelets in pairs or triplets, at least 1 spikelet in each group usually sessile; pedicels shorter or only a little longer than the sessile spikelets (FNA 25:602) | Andropogoneae |
4. Spikelets either with other than 2 florets or, if with 2, the lower floret bisexual or the upper floret awned from the back or base of the lemma, or the spikelets bulbiferous; glumes usually membranous; lemmas scarious to indurate; rachilla sometimes prolonged beyond the distal floret. | → 6 |
6. Spikelets with 1 floret; lemmas terminating in a 3-branched awn (the lateral branches sometimes greatly reduced); callus well developed; ligules usually of hairs, sometimes ciliate membranes, the cilia longer than the membranous base (Aristidoideae; FNA 25:314) | Aristideae |
6. Spikelets with more than 1 floret or, if only 1, the lemma not terminating in a 3-branched awn; callus development various; ligules various. | → 7 |
7. Spikelets with 1 sexual floret or the spikelets bulbiferous; glumes absent or less than ¼ as long as the adjacent floret; lower glumes, if present, without veins, upper glumes, if present, veinless or 1-veined. | → 8 |
8. Upper glumes present, 1-veined; lower glumes absent or much shorter than the upper glumes and lacking veins (Pooideae, in part; FNA 24:57) | Brachyelytreae |
8. Both glumes absent or lacking veins. | → 9 |
9. Inflorescences 1-sided spikes; triangular in cross section, [Pooideae, in part; FNA 24:62) | Nardeae |
9. Inflorescences panicles; spikelets laterally compressed or terete. | → 10 |
10. Culms aerenchymatous, 20-500 cm long; plants of wet places, often emergent, sometimes floating; lemmas of the bisexual or pistillate florets 3-14-veined; paleas 3-10-veined (Ehrhartoideae, in part; FNA 24:36) | Oryzeae |
10. Culms not aerenchymatous, 2-300 cm tall; plants of wet or dry habitats but not emergent or floating; lemmas of the bisexual or pistillate florets 1-3-veined; paleas 2-veined. | → 11 |
11. Culms 2-19 cm tall; plants of cold or damp habitats, not rhizomatous; sheaths of the flag leaves closed for at least 1/2 their length; caryopses exposed at maturity (Pooideae, in part; FNA 24:378) | Poeae |
11. Culms 5-300 cm tall; plants usually of warm or dry habitats, often rhizomatous; sheaths of the flag leaves open to the base; caryopses not exposed at maturity (Chloridoideae, in part; FNA 25:14) | Cynodonteae |
7. Spikelets usually with more than 1 sexual floret; usually with 2 glumes, 1 or both glumes often longer than ¼ the length of the adjacent floret and/or with more than 1 vein, always longer in taxa with 1 sexual floret. | → 12 |
12. Lemmas unawned, flabellate or with (5)7-15 awnlike teeth (Chloridoideae, in part). | → 13 |
13. Plants not viscid, usually perennial; ligules present, composed of hairs (FNA 25:285) | Pappophoreae |
13. Plants viscid annuals; ligules absent (FNA 25:290) | Orcuttieae |
12. Lemmas awned or unawned, lanceolate, rectangular, or ovate, apices entire, mucronate, bilobed, or bifid, occasionally 4-lobed or 4-5-toothed, sometimes erose. | → 14 |
14. Cauline leaf sheaths closed for 1/2 their length or more; glumes usually exceeded by the distal florets, sometimes greatly so (Pooideae, in part). | → 15 |
15. Spikelets 5-80 mm long, not bulbiferous; lemmas usually awned, often bilobed or bifid, veins convergent distally; ovary apices hairy (FNA 24:193) | Bromeae |
15. Spikelets 0.7-60 mm long, sometimes bulbiferous; lemmas often unawned, not both bilobed/bifid and with convergent veins; ovary apices usually glabrous. | → 16 |
16. Lemma veins (4)5-15, usually prominent, parallel distally; spikelets 2.5-60 mm long, not bulbiferous (FNA 24:67) | Meliceae |
16. Lemmas veins 1-9, often inconspicuous, usually convergent distally; spikelets 0.7-18(20) mm long, sometimes bulbiferous (FNA 24:378) | Poeae |
14. Cauline leaf sheaths open for at least 1/2 their length; glumes exceeding or exceeded by the distal florets. | → 17 |
17. Spikelets with 1 floret; lemmas terminally or subterminally awned, the junction of the awn and lemma conspicuous; rachillas not prolonged beyond the base of the floret (Pooideae, in part; FNA 24:109) | Stipeae |
17. Spikelets with 1-60 florets; lemmas unawned or awned, awns basal to terminal, if terminal or subterminal, the lemma-awn junction not conspicuous; rachillas often prolonged beyond the base of the distal floret. | → 18 |
18. Ligules, at least of the flag leaves, of hairs, a ciliate ridge or membrane bearing cilia longer than the basal ridge or membrane; leaves usually hairy on either side of the ligule; auricles absent. | → 19 |
19. Lemmas of the fertile florets with 3-11 inconspicuous veins, never glabrous, if with 3 veins, pilose throughout or with transverse rows of tufts of hair, if with 5-11 veins, the margins pilose proximally, the hairs not papillose-based; lemma apices usually bilobed or bifid and awned or mucronate from the sinus, if acute to acuminate, the lemmas pilose; awns twisted proximally (Danthonioideae; FNA 25:298) | Danthonieae |
19. Lemmas of the fertile florets usually with 1-3 conspicuous veins, sometimes with 3 inconspicuous veins or 5-11 veins, often glabrous, if with 3 veins, usually glabrous throughout or hairy over the veins, sometimes the margins with papillose-based hairs; lemma apices acute to obtuse, bilobed, or 4-lobed, often mucronate or awned from the sinuses; awns usually not twisted. | → 20 |
20. Lemmas 1-11-veined, veins glabrous or hairy, margins without papillose-based hairs; rachillas and calluses not pilose, sometimes strigose or strigulose; basal internodes of the culms not persistent, not swollen and clavate (Chloridoideae, in part; FNA 25:14) | Cynodonteae |
20. Lemmas 3(5)-veined, veins glabrous, margins sometimes with papillose-based hairs; rachillas or calluses pilose or the basal internodes of the culms persistent, often swollen and clavate (Arundinoideae, in part; FNA 25:7) | Arundineae |
18. Ligules membranous, if ciliate, the cilia shorter than the membranous base; leaves usually glabrous on either side of the ligule; auricles present or absent. | → 21 |
21. Inflorescences panicles or unilateral racemes, not spikelike, without spike-like branches; spikelets solitary, the lowest 0-4 florets in a spikelet sterile or staminate, the distal florets sexual. | → 22 |
22. Spikelets with (1)2-25 bisexual florets; all lemmas similar in size and shape; glumes and lemmas membranous (Centothecoideae). | → 23 |
23. Culms 35-150 cm tall; spikelets with (2)3-26 florets, including the lowest (0)1-4 sterile or staminate florets; lower glumes (1)2-9-veined (FNA 25:344) | Centotheceae |
23. Culms 150-400 cm tall; spikelets with 2-4 florets, including the lowest sterile floret; glumes 0-1-veined (FNA 25:349) | Thysanolaeneae |
22. Spikelets with 1 bisexual or unisexual floret; lemmas of the sterile florets usually differing in size and shape from those of the sexual floret; glumes membranous, lemmas of the sexual florets firmer. | → 24 |
24. Lemmas of the lower florets coriaceous, at least the upper exceeding the sexual floret (Ehrhartoideae, in part; FNA 24:33) | Ehrharteae |
24. Lemmas of the lower florets membranous, often both much shorter than the sexual floret, sometimes subequal to it, sometimes only 1 sterile floret present (Pooideae, in part; FNA 24:378) | Poeae |
21. Inflorescences panicles, racemes, or spikes; spikelets sometimes in pairs or triplets, sterile florets, if any, distal to the bisexual or pistillate florets. | → 25 |
25. Lemmas with 1-3 or 9-11 conspicuous veins; sheaths open; blade cross sections with Kranz leaf anatomy (Chloridoideae, in part; FNA 25:14) | Cynodonteae |
25. Lemmas with (1)3-15 often inconspicuous veins, if with 3 conspicuous veins, the sheaths closed; sheaths open or closed; blade cross sections without Kranz leaf anatomy. | → 26 |
26. Inflorescences spikes or spikelike; spikelets 1-5+ per node, at least 1 spikelet sessile or subsessile (Pooideae, in part). | → 27 |
27. Upper glumes 5-9-veined; spikelets subsessile and solitary at the nodes; auricles absent (FNA 24:187) | Brachypodieae |
27. Upper glumes 1-5-veined; spikelets 1-5+ per node, usually at least 1 sessile at each node, sometimes highly reduced branches present; auricles present or absent. | → 28 |
28. Inflorescences with 1-5 spikelets at a node, if 3, usually with 1 sessile and 2 pedicellate spikelets, if 1, the spikelet tangential to or embedded in the rachis, with 2 glumes, the glumes facing each other; ovaries with hairy apices; auricles often present (FNA 24:238) | Triticeae |
28. Inflorescences spikelike panicles with highly reduced branches, or spikes with spikelets radial to the rachises and all but the terminal spikelet with only 1 glume, or spikes with spikelets tangential to the rachises and having 2 glumes adjacent to each other; ovaries with glabrous apices; auricles usually absent (FNA 24:378) | Poeae |
26. Inflorescences panicles, with no sessile spikelets. | → 29 |
29. Caryopses with a thick pericarp forming a distinct apical knob or beak at maturity; lemmas 3(5)-veined (Pooideae, in part; FNA 24:64) | Diarrheneae |
29. Caryopses usually with a thin pericarp, never with a distinct apical beak or knob; lemmas 3-9-veined. | → 30 |
30. Glumes subulate, stiff; lemmas unawned or with awns to 4 mm long (Pooideae, in part; FNA 24:238) | Triticeae |
30. Glumes lanceolate, membranous; lemmas awned or unawned, awn length varied. | → 31 |
31. Rachillas hairy, hairs 2-3 mm long; lemmas coriaceous; plants established in California, sometimes cultivated as ornamentals (Pooideae, in part; FNA 24:109) | Stipeae |
31. Rachillas glabrous to hairy, hairs shorter than 2 mm; lemmas membranous to coriaceous; plants native, established, or cultivated. | → 32 |
32. Leaves to 2 cm wide, usually not conspicuously distichous; culms 0.01-2.75 m tall, usually less than 1 cm thick (Pooideae, in part; FNA 24:378) | Poeae |
32. Leaves 2-10 cm wide, often conspicuously distichous; culms 2-10(15) m tall, often more than 1 cm thick. | → 33 |
33. Lower cauline blades disarticulating, upper cauline blades forming a flat, fan-shaped arrangement (Panicoideae, in part; FNA 25:352) | Gynerieae |
33. Lower cauline blades persistent, upper cauline blades not forming a flat, fan-shaped arrangement (Arundinoideae, in part; FNA 25:7) | Arundineae |
1. Leaves smelling of lemon oil or citronella, the sheaths without glandular depressions on the keel; plants perennial, not reaching reproductive maturity in the Flora region when grown outdoors | Cymbopogon |
1. Leaves usually not aromatic or, if aromatic and smelling of citronella, the sheaths with glandular depressions along the keel and plants annual; plants reaching reproductive maturity in the Flora region. | → 2 |
2. All spikelets unisexual, the pistillate and staminate spikelets in separate inflorescences or the pistillate spikelets below the staminate spikelets in the same inflorescence. | → 3 |
3. Pistillate spikelets completely concealed within a hard, globose, beadlike structure (a modified leaf sheath) from which the staminate rames protrude | Coix |
3. Pistillate spikelets exposed or enclosed by 1 or more subtending leaf sheaths and a hyaline prophyll; staminate spikelets either distal on the same branch or in a separate inflorescence on the same plant. | → 4 |
4. Staminate and pistillate spikelets in the same inflorescence and on the same branch, the staminate spikelets distal to the pistillate spikelets | Tripsacum |
4. Staminate and pistillate inflorescences usually separate; staminate inflorescences terminal on the culms and branches; pistillate inflorescences terminal on axillary peduncles, sometimes aggregated in false panicles | Zea |
2. Some spikelets bisexual (usually the sessile or more shortly pedicellate spikelet of each spikelet pair or triplet). | → 5 |
5. Spikelets apparently solitary and sessile, the pedicellate spikelets absent; pedicels absent or present. | → 6 |
6. Culms decumbent, scrambling; leaf blades ovate to ovate-lanceolate; pedicels absent or shorter than 3 mm | Arthraxon |
6. Culms erect; leaf blades lanceolate to linear-lanceolate; pedicels always present, usually longer than 3 mm. | → 7 |
7. Inflorescences terminal and axillary, composed of digitate clusters of 1-13 rames on a common peduncle; peduncles subtended by, and often partially included in, a modified leaf | Andropogon |
7. Inflorescences terminal, with elongate rachises and brancheswith several to many rames; peduncles and branches not subtended by a modified leaf | Sorghastrum |
5. Spikelets in sessile-pedicellate or unequally pedicellate pairs or triplets, the pedicellate spikelets often smaller than the sessile spikelets, sometimes rudimentary. | → 8 |
8. Pedicels strongly appressed or fused to the thick rame axes, or the rames with only 1 spikelet unit, this a triplet with 2 unequally pedicellate spikelets; bisexual spikelets usually unawned; inflorescences of rames. | → 9 |
9. Lower glumes of the sessile spikelets rugose, pitted, tuberculate, or alveolate or the keels winged or with spinelike projections at the base. | → 10 |
10. Keels of the lower glumes with spinelike projections on the base, sometimes winged distally, the surface between the keels smooth; spikelets unawned | Eremochloa |
10. Keels of the lower glumes winged throughout or not winged, the surface between the keels rough, rugose, pitted, tuberculate, or alveolate; spikelets unawned or awned. | → 11 |
11. Sessile spikelets awned | Ischaemum |
11. Sessile spikelets unawned. | → 12 |
12. Plants perennial; sessile spikelets ovate, the lower glumes smooth, rugose, or pitted | Coelorachis |
12. Plants annual; sessile spikelets hemispherical, the lower glumes alveolate | Hackelochloa |
9. Lower glumes of the sessile spikelets smooth or scabrous, not sculptured, the keels without spinelike projections. | → 13 |
13. Inflorescences false panicles; individual rames to 1 cm long, with 1 spikelet unit; spikelet units composed of 1 sessile and 2 unequally pedicellate and dissimilar spikelets | Apluda |
13. Inflorescences usually solitary rames, sometimes with 2 rames in a digitate cluster; individual rames 2-15 cm long, with more than 1 spikelet unit; spikelet units composed of sessile pedicellate pairs, the pedicellate spikelets often rudimentary or absent. | → 14 |
14. Pedicels appressed, but not fused, to the rame axes. | → 15 |
15. Pedicellate spikelets 1-3 mm long | Coelorachis |
15. Pedicellate spikelets 4-8 mm long | Elionurus |
14. Pedicels at least partially fused to the rame axes. | → 16 |
16. Plants perennial; sheaths mostly glabrous, sparsely ciliate basally | Hemarthria |
16. Plants annual; sheaths with stiff, papillose-based hairs 1-3 mm long | Rottboellia |
8. Pedicels free; rame or branch internodes slender, sometimes thickened distally; bisexual spikelets usually awned; inflorescences of rames with the spikelets in sessile-pedicellate pairs or of non-disarticulating branches with the spikelets in unequally pedicellate pairs. | → 17 |
17. All spikelet units homogamous, frequently also homomorphic. | → 18 |
18. Terminal inflorescences a single rame or a digitate or subdigitate cluster of rames. | → 19 |
19. Terminal inflorescences a digitate or subdigitate cluster of (1)2-6 rames; rames 3-7 cm long | Microstegium |
19. Terminal inflorescences solitary rames; rames 2-3 cm long | Polytrias |
18. Terminal inflorescences with elongated rachises. | → 20 |
20. Spikelets in unequally pedicellate pairs; disarticulation below the glumes, the branches remaining intact at maturity. | → 21 |
21. Spikelets usually awned; inflorescence branches usually 7-35 cm long | Miscanthus |
21. Spikelets unawned; inflorescence branches 1-7 cm long | Imperata |
20. Spikelets in sessile-pedicellate pairs or triplets; disarticulation in the rames, below the sessile spikelets. | → 22 |
22. Culms to 100 cm tall, often decumbent and straggling; terminal inflorescences composed of 2-6 subdigitately to racemosely arranged rames | Microstegium |
22. Culms 40-600 cm tall, erect; terminal inflorescences panicles, with more than 6 primary branches; branches usuallywith 2 or more rames. | → 23 |
23. Panicle branches alternate, with multiple rames; rames with more than 5 spikelet units | Saccharum |
23. Panicle branches subverticillate, with 1-3 rames; rames with 2-5 spikelet units | Spodiopogon |
17. All or most spikelet units heterogamous, usually also heteromorphic, sometimes the proximal units on the rames or racemes homomorphic and homogamous. | → 24 |
24. Terminal inflorescences with elongated rachises. | → 25 |
25. Rame internodes and pedicels with a translucent median line | Bothriochloa |
25. Rame internodes and pedicels without a translucent median line. | → 26 |
26. Sessile spikelets terete or laterally compressed, calluses usually sharp, sometimes blunt | Chrysopogon |
26. Sessile spikelets dorsally compressed, calluses usually blunt, sometimes sharp | Sorghum |
24. Terminal inflorescences and individual inflorescence units without elongated rachises, composed of 1-13 rames, or a raceme in which disarticulation occurs below the pedicellate spikelets. | → 27 |
27. Inflorescences composed of rames, disarticulation being in the rame axes; rame internodes and pedicels with a translucent median groove | Bothriochloa |
27. Inflorescences composed of rames, with disarticulation in the axes or a spikelike raceme (occasionally of 2 subdigitate spikelike branches) with disarticulation below the pedicellate spiklets; inflorescence internodes and pedicels without a translucent median groove. | → 28 |
28. All spikelet units in the inflorescence heterogamous. | → 29 |
29. Disarticulation occurring below the pedicellate spikelets, not in the inflorescence axes; pedicellate spikelets bisexual and awned, awns (4)6-15 cm long, pilose on the column, the hairs 1-2 mm long; sessile or subsessile spikelets staminate or sterile, unawned | Trachypogon |
29. Disarticulation occurring below the sessile spikelets, in the inflorescence axes; pedicellate spikelets staminate, sterile, rudimentary, or absent, unawned or with awns to 6 mm long; sessile spikelets bisexual or pistillate, awned. | → 30 |
30. Rames usually solitary on the peduncles, occasionally 2; rame internodes cupulate or fimbriate distally; lower glumes of the sessile spikelets veined between the keels | Schizachyrium |
30. Rames usually 2-13 on the peduncles, occasionally solitary; rame internodes neither fimbriate nor cupulate distally; lower glumes of the sessile spikelets usually without veins between the keels | Andropogon |
28. Basal spikelet units on each rame homomorphic and homogamous, sterile or staminate, unawned. | → 31 |
31. Awns 5-15 cm long; rames with 3-10 homogamous spikelet units | Heteropogon |
31. Awns 1-5(19) cm long; rames with 1-2 homogamous spikelet units. | → 32 |
32. Inflorescences terminal on the culms, axillary inflorescences not present or few in number | Dichanthium |
32. Inflorescences terminal and axillary, axillary inflorescences numerous. | → 33 |
33. Homogamous spikelets distinctive, forming an involucre around the rame bases | Themeda |
33. Homogamous spikelets not distinctive, not forming an involucre around the rame bases | Hyparrhenia |
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