The grass genera of the world
~ Muhlenbergia sensu lato
Including Pleopogon Nutt
Habit, vegetative morphology. Perennial; caespitose. Culms 20–100 cm high; herbaceous. Culm internodes solid. Leaves mostly basal, or not basally aggregated; non-auriculate. Sheath margins free. Sheaths laterally compressed, keeled. Leaf blades linear; narrow; 0.5–3 mm wide; flat, or folded; without abaxial multicellular glands; not pseudopetiolate; without cross venation. Ligule present; an unfringed membrane; not truncate (pointed).
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; hermaphrodite and male-only, or hermaphrodite and sterile (the lower of each pair sterile or staminate).
Inflorescence. Inflorescence a false spike, with spikelets on contracted axes, or paniculate; contracted; spicate (and bristly, the branches short); espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes disarticulating; falling entire (the short branches shed). Spikelets paired (the lower sterile or staminate, the other hermaphrodite); not secund; shortly pedicellate; consistently in long-and-short combinations, or not in distinct long-and-short combinations.
Female-sterile spikelets. The lower spikelet similar to the upper, sterile or male.
Female-fertile spikelets. Spikelets subcylindrical; compressed laterally to not noticeably compressed; falling with the glumes (deciduous in pairs). Rachilla terminated by a female-fertile floret.
Glumes present; two; more or less equal; shorter than the adjacent lemmas, or long relative to the adjacent lemmas; awned; very dissimilar (the lower usually with 2–3 slender awns, the upper 1-awned). Lower glume 2 nerved, or 3 nerved. Upper glume 1 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.
Female-fertile florets 1 (the sterile spikelets also 1-flowered). Lemmas tapering into the awn; decidedly firmer than the glumes; not becoming indurated (firm); entire; pointed; awned. Awns 1; median; apical; non-geniculate (slender); much shorter than the body of the lemma to much longer than the body of the lemma. Lemmas without a germination flap; 3 nerved. Palea present; relatively long; awnless, without apical setae; thinner than the lemma. Lodicules present; 2; free; not or scarcely vascularized. Stamens 3. Anthers 1 mm long. Ovary apically glabrous. Styles free to their bases. Stigmas 2 (short).
Fruit, embryo and seedling. Fruit fusiform. Pericarp fused. Embryo large; with an epiblast; with a scutellar tail; with an elongated mesocotyl internode. Embryonic leaf margins meeting.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; intercostal. Intercostal papillae over-arching the stomata (in places, at one end or from the side); consisting of one oblique swelling per cell (mostly at one end of each interstomatal, and sometimes in the middle of a long-cell). Long-cells markedly different in shape costally and intercostally (the costals being much narrower and more regularly rectangular). Intercostal zones exhibiting many atypical long-cells (many being quite short). Mid-intercostal long-cells rectangular and fusiform; having straight or only gently undulating walls. Microhairs present; elongated; clearly two-celled; chloridoid-type (the basal cells somewhat the longer). Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhairs (37.5–)45–46.5(–49.5) microns long. Microhair basal cells 30 microns long. Microhairs 15.6–16.5–17.4 microns wide at the septum. Microhair total length/width at septum 2.3–2.9. Microhair apical cells (10.5–)11.4–12(–18) microns long. Microhair apical cell/total length ratio 0.28–0.36. Stomata common; 21–24 microns long. Subsidiaries dome-shaped (mostly), or triangular (a few). Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare (ignoring the hair bases); not paired. Intercostal silica bodies absent. Short macrohairs common. Crown cells absent. Costal short-cells conspicuously in long rows. Costal silica bodies present in alternate cell files of the costal zones; saddle shaped (squarish to tall-and-narrow versions of this form predominating), or tall-and-narrow; not sharp-pointed.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+. PCR sheath outlines even. PCR sheaths of the primary vascular bundles interrupted; interrupted both abaxially and adaxially. PCR sheath extensions absent. PCR cell chloroplasts centripetal. Mesophyll with radiate chlorenchyma; traversed by columns of colourless mesophyll cells (conspicuously, from every furrow). Leaf blade nodular in section, or adaxially flat; with the ribs more or less constant in size (low). Midrib conspicuous; with one bundle only. Bulliforms present in discrete, regular adaxial groups; associated with colourless mesophyll cells to form deeply-penetrating fans (these linked with traversing columns of colourless cells). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with the primaries only - the rest with strands only); forming figures (the primaries with Is). Sclerenchyma all associated with vascular bundles. The lamina margins with fibres.
Cytology. Chromosome base number, x = 10. 2n = 28 and 40.
Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Cynodonteae; Muhlenbergiinae (as a synonym of Muhlenbergia). 3 species.
Distribution, phytogeography, ecology. Southern U.S.A., Hawaii to north tropical South America.
Species of open habitats. Plains and rocky hills.
Economic aspects. Important native pasture species: L. phleoides.
Rusts and smuts. Rusts Puccinia. Taxonomically wide-ranging species: Puccinia schedonnardi. Smuts from Ustilaginaceae. Ustilaginaceae Ustilago.
References, etc. Leaf anatomical: this project.
Illustrations. • L. phleoides: Hitchcock (1920), Genera of U.S. Grasses. • L. setosus: Nicora & Rúgolo de Agrasar (1987)
We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, and classifications. See also Guidelines for using data taken from Web publications.
Cite this publication as: ‘Watson, L., Macfarlane, T.D., and Dallwitz, M.J. 1992 onwards. The grass genera of the world: descriptions, illustrations, identification, and information retrieval; including synonyms, morphology, anatomy, physiology, phytochemistry, cytology, classification, pathogens, world and local distribution, and references. Version: 13th November 2017. delta-intkey.com/grass’.