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The grass genera of the world

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

Micraira F. Muell.

Habit, vegetative morphology. Mat-forming perennial (polytrichoid in appearance). Culms 1–9 cm high; herbaceous. Leaves not basally aggregated; spirally disposed; non-auriculate. Leaf blades narrow; cordate, or not cordate, not sagittate; setaceous to not setaceous (pungent or muticous); pseudopetiolate, or not pseudopetiolate; without cross venation; disarticulating from the sheaths. Ligule a fringed membrane to a fringe of hairs.

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

Inflorescence. Inflorescence a single spike, or a single raceme, or paniculate; open, or contracted; with capillary branchlets; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate; not in distinct ‘long-and-short’ combinations.

Female-fertile spikelets. Spikelets 0.75–2 mm long; compressed laterally; disarticulating above the glumes. Rachilla prolonged beyond the uppermost female-fertile floret. Hairy callus absent.

Glumes two; more or less equal; shorter than the spikelets to exceeding the spikelets; shorter than the adjacent lemmas to long relative to the adjacent lemmas; pointed; awnless (muticous, mucronate or mucronulate); similar (membranous). Lower glume 1 nerved. Upper glume 1 nerved. Spikelets with female-fertile florets only, or with incomplete florets. The incomplete florets proximal to the female-fertile florets. The proximal incomplete florets 1; male, or sterile. The proximal lemmas awnless; 5–9 nerved; more or less equalling the female-fertile lemmas; similar in texture to the female-fertile lemmas; not becoming indurated.

Female-fertile florets 1–2. Lemmas almost rectangular; less firm than the glumes (thinly membranous to hyaline); not becoming indurated; entire; blunt; awnless; hairless; carinate to non-carinate; 5–9 nerved. Palea present; relatively long, or conspicuous but relatively short, or very reduced (almost rectangular); entire to deeply bifid; awnless, without apical setae; thinner than the lemma to textured like the lemma; not indurated; 2-nerved, or several nerved (2, or 5–7); 2-keeled. Lodicules absent. Stamens 2. Anthers 0.5–1.2 mm long; not penicillate. Ovary apically glabrous. Stigmas 2; red pigmented.

Fruit, embryo and seedling. Fruit small (0.3–0.75 mm long); ellipsoid; compressed dorsiventrally. Hilum long-linear. Embryo small. Endosperm containing only simple starch grains. Embryo without an epiblast; with a scutellar tail.

First seedling leaf with a well-developed lamina. The lamina narrow; curved.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present, or absent (e.g., M. subulifolia). Intercostal papillae not over-arching the stomata; several per cell (small, up to 15 per cell). Long-cells similar in shape costally and intercostally (but the costals rather smaller); of similar wall thickness costally and intercostally (thin walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls, or having straight or only gently undulating walls. Microhairs present; panicoid-type; (36–)45–51 microns long; 3.6–6.5(–8.4) microns wide at the septum. Microhair total length/width at septum 6.1–13.3. Microhair apical cells (16.5–)22.5–24(–25.5) microns long. Microhair apical cell/total length ratio 0.46–0.55. Stomata absent or very rare, or common; 18–24 microns long. Subsidiaries dome-shaped. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare; not paired (rare); not silicified. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’; short, angular, butterfly shaped, or dumb-bell shaped, or cross shaped; sharp-pointed (all the silica-bodies angular, many more or less rectangular - cf. Pheidochloa, but not vertically elongated).

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; Isachne-type, or not Isachne-type (e.g., M. subulifolia). Leaf blade 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): Arundinoideae; Micraireae. Soreng et al. (2015): Micrairoideae; Micraireae. 13 species.

Distribution, phytogeography, ecology. Australia.

Rocky places, in shallow soils.

References, etc. Morphological/taxonomic: Clifford 1964; Lazarides 1979, 1985. Leaf anatomical: Metcalfe 1960; this project.

Illustrations. • M. compacta, M. subspicata: Lazarides, 1979. • M. tenuis, M. adamsii, M. dentata, M. pungens: Lazarides, 1979. • Spiral phyllotaxy (M. subspicata). • Leafy shoot. Micraira sp. Spiral phyllotaxy, with (below) leaf blades disarticulated from sheaths. • General aspect (M. stipoides). • M. subulifolia: Hook. Ic. Pl. 14 (1880–82). • M. subulifolia, 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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