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The grass genera of the world

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

Microchloa R.Br.

From the Greek mikros (small) and chloe (a grass).

Type species: Type: M. indica (L.f.) P.Beauv.

Including Micropogon Pfeiffer

Excluding Rendlia

Habit, vegetative morphology. Annual (rarely), or perennial; caespitose (low), or decumbent (mat-forming). Culms 5–60 cm high; herbaceous; branched above (M. annua), or unbranched above. The branching simple. Culm nodes glabrous. Culm internodes solid. Leaves mostly basal, or not basally aggregated; non-auriculate. Leaf blades narrow (stiff, often convolute); setaceous, or not setaceous; without abaxial multicellular glands; not pseudopetiolate; without cross venation; persistent. Ligule a fringed membrane (narrow), or a fringe of hairs.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets; exposed-cleistogamous, or chasmogamous (?).

Inflorescence. Inflorescence a single spike (slender, often curved, the spikelets inclined to pectinate). Rachides hollowed (crescentic in section), or hollowed and winged. Inflorescence espatheate (but often embraced by the uppermost sheath); not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent (tough, narrow). Spikelets solitary; secund; biseriate; sessile.

Female-fertile spikelets. Spikelets 1.7–5.5 mm long; adaxial (but twisted); not noticeably compressed to compressed dorsiventrally; disarticulating above the glumes. Rachilla terminated by a female-fertile floret. Hairy callus present. Callus short; pointed.

Glumes two; more or less equal; exceeding the spikelets; long relative to the adjacent lemmas; lateral to the rachis; hairless; glabrous; pointed (lanceolate-acute); awnless; very dissimilar (the lower asymmetric, cymbiform, keeled, twisted at the base, the upper flat). Lower glume 1 nerved. Upper glume 1 nerved. Spikelets with female-fertile florets only.

Female-fertile florets 1. Lemmas not becoming indurated (membranous or hyaline); entire to incised; when entire pointed, or blunt; not deeply cleft (no more than emarginate); awnless, or mucronate; hairy (ciliate on the nerves); carinate to non-carinate; without a germination flap; 2 nerved. Palea present; entire to apically notched; awnless, without apical setae; textured like the lemma; not indurated; 2-nerved; 2-keeled. Palea keels hairy. Lodicules present; 2; free; fleshy; glabrous. Stamens 3. Anthers relatively long; not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit free from both lemma and palea; small (0.9–1.5 mm long); ellipsoid; compressed dorsiventrally, or not noticeably compressed. Hilum short. Pericarp fused. Embryo large; not waisted. Endosperm hard; without lipid. Embryo with an epiblast; with a scutellar tail; with an elongated mesocotyl internode. Embryonic leaf margins meeting.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; more or less spherical, or elongated; ostensibly one-celled, or clearly two-celled (?); chloridoid-type. Stomata common; 21.6–27 microns long. Subsidiaries triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs (rarely), or not paired (usually solitary); silicified, or not silicified. Intercostal silica bodies absent. Costal short-cells conspicuously in long rows. Costal silica bodies present in alternate cell files of the costal zones; saddle shaped; not sharp-pointed.

Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.

C4; XyMS+. PCR sheath outlines uneven, or even. PCR sheaths of the primary vascular bundles complete to interrupted; interrupted abaxially only. PCR sheath extensions absent. PCR cell chloroplasts centrifugal/peripheral (usually), or centripetal (in some individuals of M. caffra?). Mesophyll with radiate chlorenchyma; traversed by columns of colourless mesophyll cells (rarely), or not traversed by colourless columns. Leaf blade adaxially flat. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups; associated with colourless mesophyll cells to form deeply-penetrating fans (these sometimes linked with traversing columns of colourless cells). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’. Sclerenchyma all associated with vascular bundles. The lamina margins without fibres.

Cytology. Chromosome base number, x = 10. 2n = 40.

Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Cynodonteae; Eleusininae. 4 species.

Distribution, phytogeography, ecology. 3 in Africa, 1 pantropical.

Mesophytic to xerophytic; species of open habitats; glycophytic. Savanna, in shallow hard soils.

Rusts and smuts. Rusts — Puccinia. Smuts from Ustilaginaceae. Ustilaginaceae — Ustilago.

References, etc. Leaf anatomical: Metcalfe 1960; studied by us - M. indica (L.f.) Beauv.

Illustrations. • General aspect (M. caffra): Gibbs Russell et al., 1990. • M. kunthii: Hitchcock and Chase (1950). • M. indica: P. Beauv. (1812). • Inflorescence of M. indica. • Inflorescence detail of M. indica. • Abaxial epidermis of leaf blade (M. indica)

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.’.