| # The grass genera of the world |

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

### Microlaena R.Br.

From the Greek mikros (small) and chlaina (cloak), alluding to spikelets with minute glumes.

~ Ehrharta

Habit, vegetative morphology. Perennial; stoloniferous and caespitose. Culms 30–200 cm high; woody and persistent, or herbaceous. Culm nodes glabrous. Culm internodes hollow. Young shoots extravaginal. Leaves not basally aggregated; auriculate, or non-auriculate; without auricular setae. Leaf blades linear to linear-lanceolate; narrow; flat (or concave); not pseudopetiolate; without cross venation; persistent; rolled in bud. Ligule an unfringed membrane to a fringed membrane (a hyaline rim, with caducous cilia). Contra-ligule absent.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality (but often cleistogamous, leading to reduced paleas and lodicules, and indehiscent stamens). Plants inbreeding; exposed-cleistogamous, or chasmogamous; with hidden cleistogenes, or without hidden cleistogenes. The hidden cleistogenes when present, in the leaf sheaths.

Inflorescence. Inflorescence a single raceme, or paniculate; open; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.

Female-fertile spikelets. Spikelets compressed laterally; disarticulating above the glumes; with a distinctly elongated rachilla internode above the glumes (i.e., beneath the empty lemmas). Rachilla terminated by a female-fertile floret; hairless. Hairy callus present.

Glumes two; very minute; very unequal (the G2 longer); shorter than the adjacent lemmas; awnless; similar (membranous). Lower glume 0–1 nerved. Upper glume 0–1 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 2 (similar); epaleate; sterile. The proximal lemmas awned (long acuminate, tapered into long slender awns); 5–9 nerved; decidedly exceeding the female-fertile lemmas; decidedly firmer than the female-fertile lemmas (cartilaginous, usually ribbed and grooved).

Female-fertile florets 1. Lemmas decidedly firmer than the glumes (cartilaginous, with thin margins); becoming indurated to not becoming indurated; entire; pointed; awnless, or mucronate, or awned (tapered into the stout awn). Awns (when present) 1; median; apical; non-geniculate; hairless (scabrid); much shorter than the body of the lemma. Lemmas hairless; carinate (scabrid-ciliate on the keel); 5–7 nerved. Palea usually present; when present, relatively long, or conspicuous but relatively short, or very reduced; entire; awnless, without apical setae; thinner than the lemma; not indurated (thinly membranous); 1-nerved (or nerveless); one-keeled, or keel-less. Palea keels wingless. Lodicules present; 2; free; membranous; ciliate, or glabrous; toothed; relatively heavily vascularized (cf. Ehrharta). Stamens 2–6. Anthers not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2; white.

Fruit, embryo and seedling. Fruit free from both lemma and palea; medium sized; oblong-linear; compressed laterally. Hilum long-linear. Embryo small; not waisted. Endosperm containing compound starch grains. Embryo with an epiblast; with a scutellar tail; with an elongated mesocotyl internode. Embryonic leaf margins overlapping.

Seedling with a short mesocotyl; with a tight coleoptile. First seedling leaf with a well-developed lamina. The lamina broad; curved; 7–9 veined.

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 and fusiform; having markedly sinuous walls (rectangular), or having straight or only gently undulating walls (fusiform). Microhairs present; panicoid-type; 36–54 microns long; 6–9.3 microns wide at the septum. Microhair total length/width at septum 4.8–9. Microhair apical cells (16–)21–33(–36) microns long. Microhair apical cell/total length ratio 0.53–0.71. Stomata common; 21–24 microns long. Subsidiaries dome-shaped, or triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common, or absent or very rare; not silicified. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’; cross shaped, or butterfly shaped, or dumb-bell shaped; not sharp-pointed.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade; without arm cells; without fusoids. Leaf blade ‘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.

Culm anatomy. Culm internode bundles in one or two rings.

Phytochemistry. Tissues of the culm bases with abundant starch. Leaves containing flavonoid sulphates (M. stipoides).

Cytology. Chromosome base number, x = 10.

Classification. Watson & Dallwitz (1994): Bambusoideae; Oryzodae; Ehrharteae. Soreng et al. (2015): Oryzoideae; Ehharteae. 10 species.

Distribution, phytogeography, ecology. Philippines, Java to Australasia.

Helophytic to mesophytic; shade species and species of open habitats.

Rusts and smuts. Rusts — Puccinia.

References, etc. Morphological/taxonomic: Willemse 1982. Leaf anatomical: Metcalfe 1960; studied by us - M. stipoides (Labill.) R. Br.

Illustrations. • Microlaena stipoides (as M. gunnii, with Ehrharta tasmanica): Hooker, Fl. Tasmaniae (1860). • General structure (Microlaena stipoides). • Characteristic spikelet base of Microlaena stipoides: this project. Microlaena stipoides. Minute glumes, long internode between them and the lemma base, hairy callus. • Lodicules and gynoecium (Microlaena stipoides). • Microlaena stipoides. abaxial epidermis of leaf blade: this project. • Microlaena stipoides, leaf blade T.S. fluorescence image: this project. • Microlaena stipoides, leaf blade T.S. fluorescence image: 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: 15th June 2025. delta-intkey.com’.

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