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The grass genera of the world

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

Triplachne Link

Habit, vegetative morphology. Annual. Culms 5–25 cm high; herbaceous. Culm nodes glabrous. Leaves non-auriculate. Leaf blades linear; narrow; 2–3 mm wide; flat; not pseudopetiolate; without cross venation; persistent. Ligule an unfringed membrane; truncate; 2–3 mm long.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.

Inflorescence. Inflorescence paniculate (1–5 cm long); contracted; spicate, or more or less ovoid; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.

Female-fertile spikelets. Spikelets 3–4.5 mm long; compressed laterally; disarticulating above the glumes. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension naked. Hairy callus present.

Glumes two; more or less equal; exceeding the spikelets; long relative to the adjacent lemmas; hairless (shiny, scabrid on the keel); pointed; awnless; carinate; similar (membranous, lanceolate, acute). Lower glume 1 nerved. Upper glume 1 nerved. Spikelets with female-fertile florets only.

Female-fertile florets 1. Lemmas truncate; somewhat saccate (gibbously ovate in profile); less firm than the glumes (scarious); not becoming indurated; entire; awned. Awns 3; median and lateral (the two outer veins excurrent, plus the median); the median different in form from the laterals; dorsal; from well down the back; geniculate; much longer than the body of the lemma; entered by one vein. The lateral awns shorter than the median (straight, via the outer, excurrent veins). Lemmas hairy (with long appressed hairs); non-carinate; obscurely 5 nerved. Palea present; relatively long; tightly clasped by the lemma; 2-nerved. Lodicules absent. Stamens 3. Anthers 0.5 mm long; not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit small. Hilum short. Embryo small.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (the costals long and narrow, the intercostals somewhat diamond-shaped and inflated); of similar wall thickness costally and intercostally. Mid-intercostal long-cells fusiform (strongly so); having straight or only gently undulating walls. Microhairs absent. Stomata common; 37–45 microns long. Subsidiaries dome-shaped, or triangular. Guard-cells overlapped by the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs and not paired (solitary); silicified (when paired), or not silicified. Costal zones with short-cells. Costal short-cells conspicuously in long rows, or neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies horizontally-elongated crenate/sinuous, or ‘panicoid-type’; not sharp-pointed.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma. Leaf blade with distinct, prominent adaxial ribs, or ‘nodular’ in section; with the ribs more or less constant in size. Midrib conspicuous; with one bundle only. Bulliforms present in discrete, regular adaxial groups; 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): Pooideae; Poodae; Aveneae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Agrostidinae. 1 species (T. nitens).

Distribution, phytogeography, ecology. Mediterranean, Canaries.

Xerophytic; species of open habitats. Near the sea.

References, etc. Leaf anatomical: studied by us.

Illustrations. • T. nitens, as Gastridium triaristatum: adapted from Vaillant (1849), Atlas de la Flore d'Algerie. • T. nitens, abaxial epidermis of leaf blade: 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: 11th December 2017.’.