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The grass genera of the world

L. Watson, T.D. Macfarlane, and M.J. Dallwitz

Spodiopogon Trin.

From the Greek spodios (ashen) and pogon (beard), perhaps referring to inflorescence hair.

Excluding Eccoilopus

Habit, vegetative morphology. Annual, or perennial. Culms 150 cm high; herbaceous; branched above, or unbranched above. The branching simple. Culm internodes solid. Leaf blades linear to lanceolate; cordate to sagittate, or not cordate, not sagittate; flat; pseudopetiolate to not pseudopetiolate; without cross venation. Ligule present; an unfringed membrane (bearded at its base).

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality (homogamous); overtly heteromorphic (the pedicelled members with imperfect lemma awns, but sometimes with awned glumes).

Inflorescence. Inflorescence paniculate; open (much branched); espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes ‘racemes’ (usually short); with very slender rachides; disarticulating; disarticulating at the joints. ‘Articles’ non-linear (clavate, with cupular pubescent apices); not appendaged; disarticulating transversely. Spikelets in triplets, or paired (all paired, or with a terminal triad); sessile and pedicellate; consistently in ‘long-and-short’ combinations; in pedicellate/sessile combinations. Pedicels of the ‘pedicellate’ spikelets free of the rachis. The ‘shorter’ spikelets hermaphrodite. The ‘longer’ spikelets hermaphrodite.

Female-fertile spikelets. Spikelets compressed dorsiventrally; falling with the glumes (the sessile members falling with adjacent joint and pedicel, the pedicellate members falling from their pedicels). Rachilla terminated by a female-fertile floret. Hairy callus present (bearded). Callus short.

Glumes two; G2 larger; long relative to the adjacent lemmas; hairy, or hairless; awned (sometimes shortly so in pedicellate spikelets), or awnless; very dissimilar (the lower glume chartaceous, pallid, with raised nerves, the upper cymbiform). Lower glume not two-keeled (the nerves equally ribbed); convex on the back; not pitted; relatively smooth; 5–9 nerved (and ridged). Upper glume 3–9 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; male, or sterile. The proximal lemmas awnless; 3 nerved; as long as spikelet, similar to G2; similar in texture to the female-fertile lemmas (hyaline); not becoming indurated.

Female-fertile florets 1. Lemmas less firm than the glumes (hyaline); not becoming indurated; incised; 2 lobed; deeply cleft (1/3–3/4); awned (but those of the pedicellate spikelets imperfectly so). Awns 1; median; from a sinus; geniculate. Lemmas non-carinate; without a germination flap; 3 nerved. Palea present; relatively long; deeply apically notched; awnless, without apical setae (margins ciliate); not indurated (hyaline). Lodicules present; 2; free; ciliate (on the larger lobe); toothed (unequally 2-lobed). Stamens 3. Ovary apically glabrous. Stigmas 2.

Fruit, embryo and seedling. Fruit fusiform; compressed laterally. Hilum short. Embryo large.

Seedling with a long mesocotyl. First seedling leaf with a well-developed lamina. The lamina broad; curved; about 41 veined.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; costal and intercostal. Intercostal papillae not over-arching the stomata (for the most part); several per cell (large, irregular, somewhat oblique, mostly in a single row per cell). Long-cells markedly different in shape costally and intercostally (the costals narrower). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; panicoid-type; 27–36 microns long; (4.5–)4.8–5.4(–6) microns wide at the septum. Microhair total length/width at septum 5–6.7. Microhair apical cells 15–21 microns long. Microhair apical cell/total length ratio 0.5–0.58. Stomata common; 22.5–30 microns long. Subsidiaries non-papillate; mostly high to low dome-shaped. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’; consistently nodular (elongated); not sharp-pointed.

Transverse section of leaf blade, physiology. C4; XyMS–. PCR sheath outlines even. PCR sheath extensions absent. PCR cell chloroplasts seemingly centripetal. Midrib very conspicuous; having a conventional arc of bundles (three large bundles, with small ones between and peripheral to them); with colourless mesophyll adaxially. The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups to not present in discrete, regular adaxial groups (epidermis mostly irregularly bulliform); in places in simple fans. Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’ (the primaries and some smaller bundles with conspicuous I’s). Sclerenchyma all associated with vascular bundles.

Cytology. 2n = 40 and 42. Chromosomes ‘small’.

Classification. Watson & Dallwitz (1994): Panicoideae; Andropogonodae; Andropogoneae; Andropogoninae. Soreng et al. (2015): Panicoideae; Andropogonodae; Andropogoneae. 10 species.

Distribution, phytogeography, ecology. Mainly temperate Asia, Middle East.

Grassy hillsides.

Rusts and smuts. Rusts — Puccinia. Taxonomically wide-ranging species: Puccinia miyoshiana. Smuts from Ustilaginaceae. Ustilaginaceae — Sorosporium, Sphacelotheca, and Ustilago.

References, etc. Leaf anatomical: Metcalfe 1960; studied by us - S. lacei Hole.

Illustrations. • S. pogonanthus: Fl. Iraq, 1968. • S. lacei, T.S. of leaf blade reduced to midrib: this project

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.’.