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The grass genera of the world

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

Polytrias Hackel

From the Greek polys (many) and trias (group of three), alluding to triplets of spikelets.

~ Eulalia (E. amaura)

Including Aethonopogon Kuntze

Habit, vegetative morphology. Creeping, mat-forming perennial; stoloniferous. Culms 10–30 cm high; herbaceous. Culm nodes glabrous. Culm internodes hollow. Leaves mostly basal; non-auriculate. Leaf blades narrow; without cross venation; persistent. Ligule a fringed membrane (short).

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets usually all alike in sexuality; more or less homomorphic (the pedicelled smaller, sometimes male-only).

Inflorescence. Inflorescence a solitary ‘raceme’; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes ‘racemes’ (many-jointed); solitary; with very slender rachides; disarticulating; disarticulating at the joints. ‘Articles’ linear; not appendaged; disarticulating obliquely; densely long-hairy (the hairs brown). Spikelets in triplets; not secund; sessile and pedicellate; consistently in ‘long-and-short’ combinations; in pedicellate/sessile combinations (two sessile, one pedicelled). Pedicels of the ‘pedicellate’ spikelets free of the rachis. The ‘shorter’ spikelets hermaphrodite. The ‘longer’ spikelets hermaphrodite (usually), or male-only.

Female-fertile spikelets. Spikelets 3.5–4.5 mm long; compressed dorsiventrally; falling with the glumes (the pedicelled falling from its pedicel, the sessile with the internode and pedicel). Rachilla terminated by a female-fertile floret. Hairy callus absent.

Glumes two; more or less equal; long relative to the adjacent lemmas; hairy; without conspicuous tufts or rows of hairs; awnless; very dissimilar (truncate, the G1 cartilaginous and 2-keeled, the G2 longer and naviculate). Lower glume two-keeled; flattened on the back to concave on the back; not pitted; relatively smooth; 4 nerved (with no median). Upper glume 3 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.

Female-fertile florets 1. Lemmas less firm than the glumes (thinly membranous); not becoming indurated; incised; 2 lobed; deeply cleft (the lobes narrow, hairy); awned. Awns 1; median; from a sinus; geniculate; much longer than the body of the lemma. Lemmas hairy (on the lobes); non-carinate; 1 nerved. Palea present; 2-nerved. Lodicules absent. Stamens 3. Anthers not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2; red pigmented.

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

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present. Intercostal papillae over-arching the stomata; several per cell (symmetrical, finger-like). Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally (thin walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; panicoid-type; (30–)31.5–36(–42) microns long; 4.2–5.4–6 microns wide at the septum. Microhair total length/width at septum 5.8–7.1. Microhair apical cells 16.5–19.5(–24) microns long. Microhair apical cell/total length ratio 0.52–0.57. Stomata common; 22.5–24 microns long. Subsidiaries triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; not paired (solitary); silicified. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’; not sharp-pointed.

Transverse section of leaf blade, physiology. C4; XyMS–. Mesophyll with radiate chlorenchyma. Leaf blade ‘nodular’ in section; with the ribs more or less constant in size. Midrib not readily distinguishable; 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): Panicoideae; Andropogonodae; Andropogoneae; Andropogoninae. Soreng et al. (2015): Panicoideae; Andropogonodae; Andropogoneae; Saccharinae. 1 species.

Distribution, phytogeography, ecology. Java.

Species of open habitats. Waste land, roadsides.

Economic aspects. Lawns and/or playing fields: in the humid tropics.

Rusts and smuts. Rusts — Puccinia. Taxonomically wide-ranging species: ‘Uromycesschoenanthi. Smuts from Ustilaginaceae. Ustilaginaceae — Ustilago.

References, etc. Leaf anatomical: this project.

Illustrations. • P. amura, 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: 13th November 2017. delta-intkey.com/grass’.

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