The grass genera of the world
~ Danthonia sensu lato
Habit, vegetative morphology. Perennial; caespitose. Culms 30–120 cm high; herbaceous; branched above, or unbranched above. Culm nodes glabrous. Culm internodes hollow. Plants unarmed. Young shoots intravaginal. Leaves not basally aggregated; auriculate (from the base of the blade). Leaf blades linear; narrow (to 8 mm wide at the base); 3–8 mm wide; setaceous (at the tips), or not setaceous; flat, or rolled (usually convolute); not pseudopetiolate; without cross venation; persistent (old basal leaves with curled blades in P. brachyphylla). Ligule a fringe of hairs; about 0.5 mm long. Contra-ligule absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence few spikeleted; paniculate (4–25 cm long); contracted (but the central axis visible); without capillary branchlets; espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; not secund; pedicellate.
Female-fertile spikelets. Spikelets 35–55 mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets; with conventional internode spacings. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Hairy callus present. Callus long; pointed.
Glumes present; two; relatively large (35–55 mm long); more or less equal; about equalling the spikelets to exceeding the spikelets; long relative to the adjacent lemmas (exceeding them); hairless; glabrous; pointed (acuminate); awnless; carinate; similar (lanceolate, membranous). Lower glume much exceeding the lowest lemma; 3 nerved, or 5(–7) nerved. Upper glume 3 nerved, or 5(–7) nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped.
Female-fertile florets 2, or 3. Lemmas decidedly firmer than the glumes (leathery); incised; basically 2 lobed (the triangular lobes themselves bifid); deeply cleft; awned. Awns 3; median and lateral; the median different in form from the laterals; from a sinus; geniculate; hairless (scabrid); much longer than the body of the lemma. The lateral awns shorter than the median (non-geniculate, loosely twisted, 10–16 mm long, from the inner margins of the lobes). Lemmas hairy (villous); non-carinate; having the margins inrolled against the palea; without a germination flap; 9 nerved; with the nerves non-confluent. Palea present (glabrous, by contrast with Pentameris); relatively long (exceeding the lemma lobes); apically notched; awnless, without apical setae; textured like the lemma (leathery); 2-nerved; 2-keeled. Palea back glabrous. Palea keels glabrous. Lodicules present; free; fleshy; ciliate (or at least ciliolate), or glabrous; heavily vascularized. Stamens 3. Anthers about 8 mm long; not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles fused (the stigmatic hairs joining over the ovary apex). Stigmas 2; brown.
Fruit, embryo and seedling. Fruit medium sized (about 6 mm long); narrowly ellipsoid; longitudinally grooved; not noticeably compressed. Hilum long-linear (more than half the grain length).
Ovule, embryology. Micropyle not noticeably oblique. Outer integument covering no more than the chalazal half of the ovule; more than two cells thick at the micropylar margin. Inner integument discontinuous distally. Synergids haustorial (strongly developed); exhibiting large, globular starch grains.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Intercostal zones with typical long-cells (though sometimes these are relativey short). Mid-intercostal long-cells rectangular, or fusiform, or rectangular and fusiform; having markedly sinuous walls, or having straight or only gently undulating walls. Microhairs absent (but present adaxially); panicoid type. Stomata absent or very rare, or common (seen only in one specimen of P. macrantha). Subsidiaries low dome-shaped. Intercostal short-cells common; in cork/silica-cell pairs; silicified. Costal short-cells conspicuously in long rows, or neither distinctly grouped into long rows nor predominantly paired (with numerous relatively long short-cells, or with numerous intervening long-cells). Costal silica bodies panicoid-type; cross shaped to dumb-bell shaped; not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade. Leaf blade with distinct, prominent adaxial ribs (with rounded sides and flat tops); with the ribs more or less constant in size to with the ribs very irregular in sizes (this being more noticeable in P. brachyphylla). Midrib not readily distinguishable (except by its position); with one bundle only. Bulliforms present in discrete, regular adaxial groups (in all the furrows); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming figures (all the main bundles with Is or Ts).
Cytology. Chromosome base number, x = 6. 2n = 12. 2 ploid.
Classification. Watson & Dallwitz (1994): Arundinoideae; Danthonieae. Soreng et al. (2015): Danthonioideae; Danthonieae. 2 species.
Distribution, phytogeography, ecology. South Africa.
Mesophytic; species of open habitats; glycophytic. Mountain Fynbos.
References, etc. Morphological/taxonomic: Conert 1971. Leaf anatomical: Ellis 1985.
Illustrations. • General aspect (P. brachyphylla): Gibbs Russell et al., 1990
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’.