Microchloa R.Br.
From the Greek mikros (small) and chloe (a grass).
Including Micropogon Pfeiffer
Excluding Rendlia
Habit, vegetative morphology. Annual (rarely), or perennial; caespitose (low), or decumbent (mat-forming). Culms 5–60 cm high; herbaceous; unbranched above. 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; without cross venation; persistent; a fringed membrane (narrow), or a fringe of hairs.
Reproductive organization. Plants bisexual, 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; not in distinct ‘long-and-short’ combinations.
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; without proximal incomplete florets.
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 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.
Taxonomy. Chloridoideae; main chloridoid assemblage.
Distribution, ecology, phytogeography. 4 species; 3 in Africa, 1 pantropical. Mesophytic to xerophytic; species of open habitats; glycophytic. Savanna, in shallow hard soils.
Holarctic, Paleotropical, Neotropical, and Australian. Madrean. African, Madagascan, and Indomalesian. Saharo-Sindian, Sudano-Angolan, West African Rainforest, and Namib-Karoo. Indian, Indo-Chinese, and Malesian. Caribbean, Central Brazilian, Pampas, and Andean. North and East Australian. Sahelo-Sudanian, Somalo-Ethiopian, South Tropical African, and Kalaharian. Tropical North and East Australian.
Rusts and smuts. Rusts — Puccinia. Smuts from Ustilaginaceae. Ustilaginaceae — Ustilago.
References, etc. Leaf anatomical: Metcalfe 1960; this project.
Illustrations. • General aspect. • Inflorescence. • Inflorescence detail. • Abaxial epidermis of leaf blade. Microchloa indica.
Cite this publication as: Watson, L., and Dallwitz, M. J. (1992 onwards). ‘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.’ http://biodiversity.uno.edu/delta/. Version: 18th August 1999. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993 onwards, 1998), and Watson and Dallwitz (1994), and Watson, Dallwitz, and Johnston (1986) should also be cited (see References).
