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The grass genera of the world

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

Sieglingia Bernh.

Named for a botanist, Siegling.

~ Danthonia

Habit, vegetative morphology. Perennial; caespitose. Culms 10–60 cm high; herbaceous; tuberous, or not tuberous. Culm nodes glabrous. Culm internodes hollow. Leaves mostly basal; non-auriculate. Leaf blades narrow; flat, or rolled; not pseudopetiolate; without cross venation; persistent; rolled in bud, or once-folded in bud. Ligule a fringe of hairs. Contra-ligule present (of hairs).

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets; inbreeding; exposed-cleistogamous, or chasmogamous; with hidden cleistogenes, or without hidden cleistogenes. The hidden cleistogenes (when present) in the leaf sheaths (sometimes basal and very modified).

Inflorescence. Inflorescence few spikeleted; a single raceme, or paniculate; open, or contracted; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets secund, or not secund; pedicellate.

Female-fertile spikelets. Spikelets 6–12(–14) mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets; with conventional internode spacings. Rachilla prolonged beyond the uppermost female-fertile floret; hairless; the rachilla extension with incomplete florets. Hairy callus present.

Glumes two; more or less equal; about equalling the spikelets; long relative to the adjacent lemmas; pointed, or not pointed; awnless; similar (rounded below, keeled above, lanceolate to ovate). Lower glume 3–5 nerved. Upper glume 3–5 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets.

Female-fertile florets 4–6. Lemmas similar in texture to the glumes to decidedly firmer than the glumes; not becoming indurated; incised; not deeply cleft; mucronate (via the central tooth); hairy (short-haired on the lower margins), or hairless. The hairs not in tufts; not in transverse rows. Lemmas non-carinate; 7–9 nerved. Palea present; relatively long; entire; awnless, without apical setae; 2-nerved; 2-keeled. Palea keels wingless (but each enlarging and progressively thickening towards the base - by contrast with Danthonia sensu stricto?). Lodicules present; fleshy; glabrous. Stamens 3. Anthers 0.2–0.4 mm long; not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit free from both lemma and palea; small; longitudinally grooved. Hilum long-linear. Embryo large (compared with Danthonia sensu stricto); waisted. Endosperm hard; without lipid. Embryo without an epiblast; with a scutellar tail; with an elongated mesocotyl internode. Embryonic leaf margins overlapping.

Seedling with a long mesocotyl; with a loose coleoptile. First seedling leaf with a well-developed lamina. The lamina narrow; 5 veined.

Ovule, embryology. Outer integument covering no more than the chalazal half of the ovule. Inner integument discontinuous distally. Synergids haustorial.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (the costals narrower); of similar wall thickness costally and intercostally (rather thick walled, and heavily pitted anticlinally and on the surface). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; panicoid-type (large); (78–)81–99(–102) microns long; (12–)12.6–15(–18) microns wide at the septum. Microhair total length/width at septum 4.3–7.9. Microhair apical cells (36–)40.5–46.5(–52.5) microns long. Microhair apical cell/total length ratio 0.44–0.52. Stomata absent or very rare (scarce in material seen), or common (see Metcalfe); 31–34 microns long. Subsidiaries dome-shaped and triangular (of the truncated type, in the material seen). Guard-cells overlapped by the interstomatals (very slightly), or overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs (and solitary); silicified. Intercostal silica bodies mostly tall-and-narrow, or crescentic (a few cubical or saddle-shaped). Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’; short dumb-bell shaped, or cross shaped; not sharp-pointed.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade; without ‘circular cells’ (but often with a region of translucent, spongy tissue in the mid-interveinal regions of the mesophyll). Leaf blade with distinct, prominent adaxial ribs to adaxially flat (the adaxial ribs very slight); with the ribs more or less constant in size. Midrib conspicuous (by virtue of the large associated hinge groups); with one bundle only. Bulliforms present in discrete, regular adaxial groups (these conspicuous, in all the slight furrows); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’ (the midrib with an anchor, the rest of the bundles with I’s). Sclerenchyma all associated with vascular bundles.

Cytology. Chromosome base number, x = 6, or 9 (?). 2n = 24, 36, and 124. 3, 4, and 14 ploid. Chromosomes ‘fairly small’.

Classification. Watson & Dallwitz (1994): Arundinoideae; Danthonieae. Soreng et al. (2015): Danthonioideae; Danthonieae. 1 species (S. decumbens).

Distribution, phytogeography, ecology. Madeira, Algeria, Europe, Asia Minor.

Commonly adventive.

Hybrids. Intergeneric hybrids with DanthoniaDanthosieglingia Domin).

Rusts and smuts. Rusts — Puccinia. Taxonomically wide-ranging species: Puccinia brachypodii.

References, etc. Leaf anatomical: Metcalfe 1960; studied by us - S. decumbens (L.) Bernh.

Illustrations. • S. decumbens (as Triodia), general aspect: Eng. Bot. (1872). • General aspect (S. decumbens): John Curtis, 1824. • S. decumbens, abaxial epidermis of leaf blade: this project

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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.’.