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The grass genera of the world

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

Dignathia Stapf

From the Greek gnathos, likening the hardened glumes to a pair of jaws or mandibles.

Habit, vegetative morphology. Annual, or perennial; caespitose. Culms (1–)5–50 cm high; herbaceous; branched above, or unbranched above. The branching suffrutescent, or simple. Plants unarmed. Leaves not basally aggregated; non-auriculate. Leaf blades narrow; 1.5–3 mm wide (to 8 cm long); not setaceous (rigid); without cross venation; rolled in bud. Ligule a fringed membrane.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; hermaphrodite and sterile; overtly heteromorphic.

Inflorescence. Inflorescence a false spike, with spikelets on contracted axes (the pedunculate branchlets each with 2–3 spikelets, the terminal one sterile and reduced to glumes, the rest fertile); contracted. Inflorescence with axes ending in spikelets. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes very much reduced (to 1–2 spikelets plus a rudiment on the curved rachis); disarticulating; falling entire (the branchlets falling complete with fertile and sterile spikelets). Spikelets not in distinct ‘long-and-short’ combinations.

Female-fertile spikelets. Spikelets 3–7 mm long; the G1 laterally contiguous with rachis; obliquely compressed laterally; falling with the glumes. Rachilla terminated by a female-fertile floret.

Glumes two; very unequal; (the upper) long relative to the adjacent lemmas (exceeding the lemma); lateral to the rachis; hairy; pointed (acute, acuminate or subulate-beaked); awned (one or both acuminate into a curved or flexuous subule); non-carinate; very dissimilar (thickened-cartilaginous dorsally with hyaline margins, G1 shorter, G2 broader and marked with green lines). Lower glume relatively smooth; several nerved. Upper glume several nerved. Spikelets with female-fertile florets only.

Female-fertile florets 1. Lemmas less firm than the glumes (hyaline-membranous); not becoming indurated; entire; pointed; awned. Awns 1; median; apical; non-geniculate; much shorter than the body of the lemma (a short slender aristule, about 1 mm long). Lemmas hairy, or hairless; carinate; 3 nerved. Palea present; relatively long; awnless, without apical setae; 2-nerved; 2-keeled. Lodicules present; 2; free; fleshy; glabrous. Stamens 3. Anthers 1–2 mm long; not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit small (1.5–2 mm long). Hilum short. Pericarp fused. Embryo large.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; intercostal (but on only some cells). Intercostal papillae not over-arching the stomata; consisting of one oblique swelling per cell, or consisting of one symmetrical projection per cell. Long-cells differing markedly in wall thickness costally and intercostally (the costals thinner). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; chloridoid-type; 27–31.5 microns long; 7.2–9 microns wide at the septum. Microhair total length/width at septum 3–4.2. Microhair apical cells 7.5–10.5 microns long. Microhair apical cell/total length ratio 0.24–0.36. Stomata common; (18–)21–24 microns long. Subsidiaries non-papillate; mostly low to high dome-shaped, or triangular (some, fairly). Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; not paired (mostly solitary); silicified. With a few costal prickles. Crown cells absent. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’; dumb-bell shaped.

Transverse section of leaf blade, physiology. C4; XyMS+. PCR sheath extensions absent. Mesophyll with radiate chlorenchyma. Leaf blade ‘nodular’ in section to adaxially flat; with the ribs more or less constant in size (slight). Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans (these deeply penetrating). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the bundles); forming ‘figures’ (all bundles). Sclerenchyma all associated with vascular bundles.

Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Cynodonteae; Gymnopogoninae. 5 species.

Distribution, phytogeography, ecology. East Africa and India.

Species of open habitats. Dry bushland.

References, etc. Morphological/taxonomic: Stapf 1911. Leaf anatomical: studied by us - D. villosa Hubbard.

Illustrations. • D. gracilis and D. hirtella: Hook. Ic. Pl. 30 (1913)

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.’.