Grasses of Montana 1 GRASSES of MONTANA 13 December 2011
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Grasses of Montana 1 GRASSES OF MONTANA 13 December 2011 Matt Lavin and Cathy Seibert, Department of Plant Sciences and Plant Pathology, Montana State University, Bozeman, Montana 59717 POACEAE (GRAMINAE) Annual or perennial, usually monoecious herbs. Stems terete, rarely flattened. Leaves basal and often cauline, alternate, linear, parallel-veined, entire, composed of a lower sheath enclosing the stem and a flat, inrolled, or folded blade. Inflorescence terminal, consisting of spikelets arranged in usually open to spike-like panicles, less commonly racemes or solitary spikes. Flowers often bisexual; each enclosed by a lemma and palea; petals and sepals reduced to 1- -6 small translucent scales (lodicules); stamens 1--6, ovary superior with 1--3 stigmas. Fruit a caryopsis, rarely an achene (as in Eragrostis and Sporobolus). The Poaceae includes about 10,035 species and 668 genera (Stevens, 2001 onward), making it one of the largest flowering plant families. Poaceae is distributed world-wide from deserts to tropical rain forests and from coastal saline areas to alpine and arctic tundra. It is one of the most economically important plant families and includes rice, wheat, barley, rye, corn, millet, and sorghum, as well as many forage, ornamental, and turf species. Poaceae is distinguished from other monocots by small flowers that are each enclosed by a lemma and palea. The flower, lemma, and palea comprise the grass floret. Florets alternate along opposites sides of a rachilla to form the grass spikelet, which is delimited by a basal pair of glumes (lemma-like but sterile bracts). Grasses show outstanding morphological diversity in the architecture of seed dispersal. Seeds may be dispersed by the fruit only (Eragrostis and Sporobolus), the floret, the entire spikelet, with a section of the inflorescence, or with the entire inflorescence. The structures aiding dispersal of the grass fruit, whether fruits or entire inflorescences, are taxonomically useful for identifying genera. This treatment is derived from local and regional floras (Barkworth et al., 2003 and 2007; Cronquist et al., 1977; Gould, 1975; Gould and Shaw, 1983; Hitchcock, 1937 & 1951; Lesica, 2002; Booth, 1950; Dorn, 1984; McGregor, 1986). Grass genera and tribes are distinguished in part by whether they are cool (C3) or warm season (C4 photosynthesis; Clayton and Renvoize 1986; Gould and Shaw 1983; Jacobs and Everett, 2000; Soderstrom et al. 1988; Stebbins and Crampton 1961; Tzvelev 1989; Kellogg 2001). We seldom use the taxonomic ranks of subspecies and varieties because many of these infraspecific taxa have neither geographical nor ecological integrity. If a phenotype is pronounced or aligns with ecology or geogeography, we tend to distinguish it as a species in this treatment. Key to the traditional groups of grass genera 1. Spikelets dorsally compressed so that the dorsal surface of the glumes and lemmas are flat, rounded and rarely keeled, the glumes or lowest lemma are more or less flat and sandwich the innermost (uppermost) floret and obscure it in side view even when under a lens; disarticulation below the glumes, at least the spikelet is the unit of dispersal; each spikelet with one fruit-producing (plump) terminal floret above one sterile (reduced) or staminate (hollow) floret 2. 1. Spikelets laterally compressed so that the glumes and lemmas are often keeled, the glumes and all the lemmas are more or less folded in half (keeled) along the midrib, the florets are generally splayed out and easily seen in side-view with a naked eye or lens; disarticulation often above the glumes; each spikelet with one or more fruit-producing (plump) floret, sometimes with sterile or staminate floret mostly above but sometimes below the fruit-producing floret 3. 2. Inflorescences of paired spikelets, one sessile and the second pedicellate (the pedicellate spikelet often reduced to a sterile floret or a small glume, or rarely entirely absent); glumes hard or bony in texture; fertile lemmas membranous, much thinner in texture than the glumes; awns usually present (sometimes early deciduous) and borne from the fertile lemmas Andropogoneae 2. Inflorescences usually without paired spikelets; glumes leafy or papery in texture, the first glume often reduced to absent; fertile lemmas hard and bony in texture, much thicker in texture than the glumes; awns when present borne from glumes or sterile lemmas Paniceae 3. Growth habit of stout reeds, mostly 2--3 m tall; leaf blades often 2 cm wide or wider; inflorescences dense plume-like panicles; ligule mostly of hairs Phragmites 3. Growth habit of slender herbs, usually <2 m tall; leaf blades much <2 cm wide; inflorescences not dense plume-like panicles; ligules various 4. 4. Inflorescences of single terminal bilateral (2-sided or distichous) spikes; both glumes present and often awn-like; spikelets attached laterally to main rachis (sides of lemmas face the main inflorescence rachis) [Elymus condensatus and Elymus flavescens of this tribe commonly develop a panicle rather than a spike, but each panicle branch is spike-like in having sessile spikelets arranged in a two-sided fashion] Triticeae Grasses of Montana 2 4. Inflorescences of racemes or open to spike-like panicles, or of laterally or digitately arranged spikes; if a single terminal bilateral spike, then only the second glume present (excepting the terminal-most spikelet) and never awn-like and the spikelets attached edge-wise (dorsally) to main rachis 5. 5. Spikelets arranged in secund lateral or digitate spikes; ligule of hairs (but Schedonnardus with a membranous one); mostly one fertile floret per spikelet Chlorideae 5. Spikelets arranged in spikes, racemes, or panicles, if secund (e.g., Beckmannia in tribe Aveneae or Dactylis in tribe Poeae) then panicle branches not in discrete linear arrays of spikelets; ligules and florets various 6. 6. 1 floret per spikelet 7. 6. >1 floret per spikelet (including sterile or rudimentary florets) 12. 7. Glumes absent, vestigial, or forming a small cup; riparian or emergent aquatic grasses Oryzeae 7. Glumes well developed; usually other than emergent aquatic grasses 8. 8. Floret bearing a tripartite awn; ligule of hairs Aristida 8. Floret unawned or bearing a single undivided awn; ligule various 9. 9. Lemma tightly rolled around palea and enclosed fruit, hardened or bony at maturity and much thicker in texture than glumes, the lemma thus appearing as the hard seed coat; lemma awned from the tip although the awn is early deciduous in some species Stipeae 9. Lemma not tightly rolled around palea and enclosed fruit, membranous at maturity and of the same texture as the glumes, the lemma thus not appearing as the hard ‘seed’ coat; lemma unawned, awned from the back, or awned from the tip 10. 10. Ligule partially or entirely a fringe of hairs, the hairs as long or longer than a sometimes-present basal membranous portion Eragrosteae 10. Ligule entirely membranous, but often toothed or split, or with a very short rim of hairs along the larger basal membranous portion 11. 11. Lemmas distinctly 3-nerved, or 1-nerved (as in some species of Muhlenbergia and all species of Sporobolus); if present, the long-awn is borne from the tip of lemma; tips of glumes surpassing the tip(s) of the floret(s) or not; spikelets disarticulating above glumes; ligule membranous or hairy; inhabiting dry or saline sites (some Muhlenbergia inhabit wet sites) and flowering during mid- to late-summer (C4 grasses); stems and leaves wiry or tough textured, some species occasionally more fragile and easily broken Eragrosteae 11. Lemmas indistinctly many-nerved (3-nerved in some species of Alopecurus); if present, the long-awn is borne from the back of lemma (Beckmannia, Cinna, and Hierochloe are very short-awned from near the tip; Apera only is with long-awn from tip); tips of glumes surpassing the tip(s) of the floret(s); spikelets disarticulating below or above glumes; ligule always membranous; inhabiting usually wet sites or flowering during the earlier part of summer (C3 grasses); stems and leaves never wiry or tough Aveneae 12. Plants dioecious, the staminate spikelets exerted well above basal leaves, the pistillate spikelets not; collar often with conspicuous long straight hairs; ligule fringed with fine teeth; rhizomes well developed and woody; older leaves usually stiff and pungent at tips, conspicuously distichous especially in fresh condition Distichlis 12. Plants mostly with bisexual spikelets but if rarely dioecious, then not with the arrangement above; collar hairless or with soft curly hairs; ligule various; rhizomes various but not woody; older leaves soft or wiry but not pungent at tips and not distichously arranged 13. 13. Ligule with a conspicuous fringe of hairs or a basal membrane fringed with hairs as long as the membrane 14. 13. Ligule entirely membranous or with a very short fringe of hairs on the larger membranous portion 15. 14. Glumes as long as the lowest (1st) floret and usually as long or longer than all florets; lemmas indistinctly many- nerved; lemma-awn somewhat flattened dorsally and distinctly twisted, and arising from just below the distinctly bifid apex of the lemma Danthonia 14. Glumes shorter than the lowest (1st) floret, if longer, then the lemmas distinctly 3-nerved; lemma-awn, if present, slender, round in cross-section, not distinctly twisted, and not arising from just below a distinctly bifid apex of the lemma Eragrosteae 15. Lemmas awned from at least the lower two-thirds of the back; if awnless, then one or both glumes longer