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The grass genera of the world

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

Danthonia DC. sensu stricto

Named in honour of E. Danthoine, a French botanist.

Type species: Type: D. spicata (L.) Roem. & Schult.

Including Brachatera Desv., Brachyathera Kuntze, Merathrepta Raf., Wilibald-Schmidtia Conrad, Sieglingia Bernhardi

Excluding Chionochloa, Dregeochloa, Erythranthera, Karroochloa, Merxmuellera, Monachather, Monostachya, Plinthanthesis, Rytidosperma, Sieglingia

Habit, vegetative morphology. Perennial; caespitose. Culms 10–100 cm high; herbaceous; unbranched above; 2–5 noded. Culm internodes hollow. Young shoots extravaginal, or intravaginal. Leaves mostly basal; non-auriculate. Leaf blades linear; narrow; without cross venation; persistent; once-folded in bud. Ligule a fringe of hairs.

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

Inflorescence. Inflorescence few spikeleted; paniculate (sometimes reduced almost to a raceme); open; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.

Female-fertile spikelets. Spikelets 8–30 mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets; with conventional internode spacings. Rachilla prolonged beyond the uppermost female-fertile floret. Hairy callus present. Callus short to long; pointed.

Glumes two; more or less equal; about equalling the spikelets to exceeding the spikelets; long relative to the adjacent lemmas; pointed; awnless; similar (papery). Lower glume 3–7 nerved. Upper glume 3–7 nerved. Spikelets with female-fertile florets only, or with incomplete florets. The incomplete florets when present, distal to the female-fertile florets. Spikelets without proximal incomplete florets.

Female-fertile florets 2–10. Lemmas similar in texture to the glumes to decidedly firmer than the glumes; not becoming indurated; incised; 2 lobed (the lobes acute, acuminate or setaceous); deeply cleft, or not deeply cleft; awned. Awns 1, or 3; median, or median and lateral; the median different in form from the laterals (when laterals present); from a sinus; geniculate; much shorter than the body of the lemma to much longer than the body of the lemma; entered by one vein. The lateral awns when present, shorter than the median to exceeding the median (straight, terminating the lobes). Lemmas nearly always hairy (indumentum in marginal strips along the lemma, and in some species scattered on the lemma backs). The hairs not in tufts; not in transverse rows. Lemmas non-carinate (rounded on the back); without a germination flap; 9 nerved. Palea present; relatively long to conspicuous but relatively short; entire to apically notched; awnless, without apical setae; not indurated; 2-nerved; 2-keeled. Palea back glabrous, or hairy. Palea keels wingless; scabrous. Lodicules present (nearly always?); 2; free; fleshy; glabrous (usually - but with some exceptions). Stamens 3. Anthers not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases; free. Style bases widely separated. Stigmas 2.

Fruit, embryo and seedling. Fruit free from both lemma and palea; small; golden-brown; obovate; longitudinally grooved; compressed dorsiventrally; glabrous; smooth. Hilum usually long-linear. Embryo small; waisted (at least, in Sieglingia). Endosperm hard; without lipid; containing compound starch grains. Embryo without an epiblast; with a scutellar tail; with an elongated mesocotyl internode. Embryonic leaf margins meeting, or overlapping (Sieglingia).

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

Ovule, embryology. Outer integument covering no more than the chalazal half of the ovule. Inner integument discontinuous distally. Synergids haustorial (strongly developed); exhibiting large, globular starch grains.

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 (in Sieglingia, these rather thick walled, and heavily pitted anticlinally and on the surface), or differing markedly in wall thickness costally and intercostally (?). Intercostal zones with typical long-cells, or exhibiting many atypical long-cells (these tending to be hexagonal). Mid-intercostal long-cells rectangular (to hexagonal); having markedly sinuous walls. Microhairs present; panicoid-type (large in Sieglingia); of Sieglingia, (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 on Sieglingia); in Sieglingia, 31–34 microns long. Subsidiaries dome-shaped and triangular (of the truncated type, in the material of Sieglingia 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 of Sieglingia mostly tall-and-narrow, or crescentic (a few cubical or saddle-shaped). Costal short-cells conspicuously in long rows (sometimes in short series as well). Costal silica bodies tall-and-narrow, or ‘panicoid-type’; when panicoid type, cross shaped, or butterfly shaped, or dumb-bell shaped, or nodular; not sharp-pointed.

Transverse section of leaf blade, physiology. C3; XyMS+. PBS cells without a suberised lamella. Mesophyll with non-radiate chlorenchyma; without adaxial palisade; without ‘circular cells’ (but in Sieglingia 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 at least somewhat conspicuous (if only by virtue of the large associated hinge groups); with one bundle only. Bulliforms present in discrete, regular adaxial groups (at the bases of the furrows); in simple fans. All the vascular bundles accompanied by sclerenchyma (except sometimes at the leaf margins). Combined sclerenchyma girders present; forming ‘figures’ (at least in the midribs). Sclerenchyma all associated with vascular bundles.

Cytology. Chromosome base number, x = 6, or 9 (?). 2n = 18, 36, and 48. 2 and 4 ploid. Chromosomes ‘usually fairly small’. Nucleoli disappearing before metaphase.

Classification. Watson & Dallwitz (1994): Arundinoideae; Danthonieae. Soreng et al. (2015): Danthonioideae; Danthonieae. About 20 species.

Distribution, phytogeography, ecology. The Northern hemisphere component of ‘Danthonia’.

Commonly adventive (D. (Sieglingia) decumbens). Mesophytic to xerophytic; species of open habitats; glycophytic. Grasslands and open woodlands, often in hilly regions.

Economic aspects. Important native pasture species: D. californica, D. compressa etc.

References, etc. Morphological/taxonomic: Blake 1972a; Jacobs 1982. Leaf anatomical: Metcalfe 1960.

Illustrations. • D. spicata: Kunth (1835)

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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.’.