The grass genera of the world
~ Rytidosperma, Danthonia sensu lato
Habit, vegetative morphology. Perennial; rhizomatous, or caespitose, or decumbent (often sward-forming). Culms 3–12 cm high; herbaceous. Culm nodes glabrous. Culm internodes hollow. Leaves mostly basal; non-auriculate. Sheath margins free. Leaf blades narrow; setaceous; flat, or folded (to 3 cm long); without cross venation; disarticulating from the sheaths. Ligule a fringed membrane (very short), or a fringe of hairs.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
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 not secund; pedicellate.
Female-fertile spikelets. Spikelets 2.5–5 mm long; compressed laterally; disarticulating above the glumes; with distinctly elongated rachilla internodes between the florets (internodes up to 1/3 as long as the lemmas). Rachilla prolonged beyond the uppermost female-fertile floret. Hairy callus absent. Callus short; blunt (flattened).
Glumes two; more or less equal; long relative to the adjacent lemmas; free; awnless; similar. Lower glume 3–5 nerved. Upper glume 3 nerved. Spikelets with female-fertile florets only, or with incomplete florets. The incomplete florets distal to the female-fertile florets. Spikelets without proximal incomplete florets.
Female-fertile florets 3–5. Lemmas not becoming indurated; incised; minutely 3 lobed; not deeply cleft (with 3 minute apical teeth); awnless; hairy, or hairless (glabrous). The hairs when present, not in tufts; not in transverse rows (scattered). Lemmas carinate to non-carinate; 7–9 nerved. Palea present; 2-nerved; 2-keeled. Palea keels hairy (ciliate). Lodicules present; 2; joined, or free; fleshy, or membranous; glabrous; toothed. Stamens 3. Anthers not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2; brown.
Fruit, embryo and seedling. Fruit small. Hilum short. Embryo large. Endosperm containing compound starch grains. Embryo without an epiblast; with a scutellar tail; with an elongated mesocotyl internode.
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; not thickened around the micropyle. Synergids haustorial; exhibiting large, globular starch grains.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally (long and narrow); of similar wall thickness costally and intercostally (thick walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; panicoid-type; 45–55.5(–60) microns long; 9.6–14.4 microns wide at the septum. Microhair total length/width at septum 3.1–5.8. Microhair apical cells 24–36 microns long. Microhair apical cell/total length ratio 0.43–0.59. Stomata absent or very rare. Subsidiaries dome-shaped, or triangular. Intercostal short-cells common; in cork/silica-cell pairs; silicified. Intercostal silica bodies mainly crescentic. Costal short-cells conspicuously in long rows, or neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies rounded (including potato-shaped), or crescentic, or panicoid-type.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with radiate chlorenchyma, or with non-radiate chlorenchyma; without adaxial palisade. Leaf blade with distinct, prominent adaxial ribs, or adaxially flat; with the ribs more or less constant in size. Midrib conspicuous, or not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups (in the furrows); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming figures. Sclerenchyma all associated with vascular bundles.
Classification. Watson & Dallwitz (1994): Arundinoideae; Danthonieae. Soreng et al. (2015): Danthonioideae; Danthonieae. 3 species.
Distribution, phytogeography, ecology. Australia, New Zealand.
Species of open habitats. Alpine.
References, etc. Morphological/taxonomic: Zotov 1963. Leaf anatomical: 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: 13th November 2017. delta-intkey.com/grass’.