The grass genera of the world
~ Muhlenbergia sensu lato
Including Schaffnera Benth.
Habit, vegetative morphology. Slender annual; caespitose. Culms 6–12 cm high; herbaceous. Culm nodes glabrous. Leaves mostly basal; non-auriculate; without auricular setae. Sheath margins free (hyaline at the edges). Leaf blades narrow; about 0.2–1 mm wide; rolled (convolute); without abaxial multicellular glands; without cross venation (but these numerous and conspicuous under the transmission microscope). Ligule an unfringed membrane; not truncate (rounded-jagged); 0.5–1 mm long. Contra-ligule absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant (the ultimate branch of the cymose fascicle with a sterile spikelet), or all alike in sexuality (?); hermaphrodite, or hermaphrodite and sterile (?).
Inflorescence. Inflorescence complex paniculate (with small cymose fascicles of spatheate peduncles, each peduncle bearing two or three spikelets, each fascicle subtended and partly enclosed by a broad-sheathed spathe with a well developed lamina); spatheate (and spatheolate); a complex of partial inflorescences and intervening foliar organs. Spikelet-bearing axes persistent. Spikelets not secund.
Female-fertile spikelets. Spikelets 5 mm long; compressed laterally; falling with the glumes; with conventional internode spacings. Rachilla terminated by a female-fertile floret. Hairy callus present (small). Callus short; blunt.
Glumes present; two; (the upper) relatively large; very unequal (the lower minute); shorter than the adjacent lemmas; hairy (G2 hairy on the nerves); (the upper) awned (with three or five awns); very dissimilar (the lower minute and vestigial, the upper 3- or 5- aristate with long, straight, spreading, scabridulous awns, often laterally hyaline-appendiculate). Upper glume 3 nerved, or 5 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.
Female-fertile florets 1. Lemmas similar in texture to the glumes (membranous); smooth; not becoming indurated; entire to incised; when incised, 2 lobed; not deeply cleft (bilobed); awned. Awns 1; median; dorsal; from near the top; non-geniculate; somewhat recurving; hairless (scabrid); much shorter than the body of the lemma (about half as long); entered by one vein. Lemmas hairy; carinate; without a germination flap; 3 nerved. Palea present (lanceolate); relatively long; convolute around the flower; entire (blunt); awnless, without apical setae (glabrous); not indurated (hyaline); 2-nerved; keel-less (the margins embracing the flower). Lodicules absent. Stamens 3; with free filaments (these short). Anthers relatively very long; not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles fused (the ovary attenuate into one long style). Stigmas 2.
Fruit, embryo and seedling. Fruit small; ellipsoid; compressed laterally. Pericarp fused.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; intercostal (mainly on the interstomatals). Intercostal papillae not over-arching the stomata (but almost); consisting of one oblique swelling per cell (large). Mid-intercostal long-cells rectangular; having markedly sinuous walls (coarsely so). Microhairs present (very scarce); chloridoid-type (basal cell somewhat elongated). Stomata common; 15–18 microns long. Subsidiaries high dome-shaped, or triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare. Intercostal silica bodies absent. Costal short-cells conspicuously in long rows. Costal silica bodies present in alternate cell files of the costal zones; rounded (a few, round to almost rectangular), or panicoid-type (mostly); mostly rather rectangular cross shaped and butterfly shaped; not sharp-pointed.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+. PCR sheaths of the primary vascular bundles complete. PCR sheath extensions absent. Leaf blade nodular in section. Midrib conspicuous (with a fairly heavy sclerenchymatous keel); with one bundle only. Bulliforms not present in discrete, regular adaxial groups (the adaxial epidermis apparently being mainly of papillate and bulliform cells). Many of the smallest vascular bundles unaccompanied by sclerenchyma (most bundles unaccompanied by sclerenchyma: a few of the larger laterals with small abaxial strands, the midrib with a large abaxial strand (or girder?)). Combined sclerenchyma girders absent. Sclerenchyma all associated with vascular bundles.
Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage (superficially of andropogonoid appearance). Soreng et al. (2015): Chloridoideae; Cynodonteae; Muhlenbergiinae (as a synonym of Muhlenbergia). 1 species (S. gracilis).
Distribution, phytogeography, ecology. Central America.
References, etc. Morphological/taxonomic: Bentham 1882. Leaf anatomical: studied by us.
Illustrations. • S. gracilis, as Schaffnera: Hook. Ic. Pl. 14 (1880)
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: 11th December 2017. delta-intkey.com/grass’.