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The grass genera of the world

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

Yakirra Lazarides & R. Webster

Yakirra: aboriginal name for some of the species.

~ Ichnanthus australiensis and relatives

Type species: Type: Y. pauciflora (R.Br.) Lazarides & R.D.Webster.

Habit, vegetative morphology. Annual, or perennial; caespitose. Culms 8–75 cm high; herbaceous; sparsely to amply branched above, or unbranched above. The branching simple. Culm nodes hairy, or glabrous. Culm leaf sheaths rounded. Culm internodes solid, or hollow. Leaves not basally aggregated; non-auriculate. Leaf blades linear to lanceolate; narrow; 1.5–7 mm wide (3–30 cm long); flat, or rolled; without cross venation. Ligule present; a fringe of hairs.

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

Inflorescence. Inflorescence paniculate (rarely, reduced to racemes - e.g. in Y. australiensis); open, or contracted. Primary inflorescence branches inserted all around the main axis. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; not secund; pedicellate. Pedicel apices cupuliform.

Female-fertile spikelets. Spikelets 3.2–6.8 mm long; oblong, or elliptic, or obovate, or oblanceolate; adaxial (when appressed); compressed dorsiventrally; disarticulating above the glumes, or falling with the glumes; with a distinctly elongated rachilla internode between the glumes and with distinctly elongated rachilla internodes between the florets (the latter being a straight, swollen elaiosome). The upper floret conspicuously stipitate. The stipe beneath the upper floret not filiform; straight and swollen; homogeneous. Rachilla terminated by a female-fertile floret. Hairy callus absent.

Glumes present; two; very unequal; (the upper) long relative to the adjacent lemmas; hairy (with adaxial hairs at the apex of G2); (the lower) with distinct rows of hairs (with a transverse row of setae); pointed (acuminate to acute, ovate, elliptic to oblanceolate); awnless; non-carinate; membranous. Lower glume 3–9 nerved. Upper glume 5–9 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; paleate. Palea of the proximal incomplete florets fully developed to reduced. The proximal incomplete florets sterile. The proximal lemmas awnless; 5–9 nerved (elliptic to oblanceolate, acute to acuminate); longer than the fertile lemmas; less firm than the female-fertile lemmas (membranous); not becoming indurated.

Female-fertile florets 1. Lemmas acute; decidedly firmer than the glumes; smooth; becoming indurated; yellow in fruit, or brown in fruit; entire; pointed; awnless; hairless; glabrous; non-carinate (dorsally rounded); having the margins inrolled against the palea; with a clear germination flap; with strong nerves. Palea present; relatively long; entire; awnless, without apical setae; indurated; 2-nerved. Lodicules present; 2; fleshy; glabrous. Stamens 3. Ovary apically glabrous. Styles free to their bases. Stigmas 2; red pigmented.

Fruit, embryo and seedling. Fruit small; compressed dorsiventrally. Hilum short. Embryo large.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Mid-intercostal long-cells having markedly sinuous walls. Microhairs present; panicoid-type; (39–)42–51 microns long; (4.5–)5.1–7.5 microns wide at the septum. Microhair total length/width at septum 5.9–10.7. Microhair apical cells (18–)19.5–28.5(–30) microns long. Microhair apical cell/total length ratio 0.46–0.62. Stomata common; (33–)36–48(–51) microns long. Subsidiaries dome-shaped and triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common. Costal zones with short-cells. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’; not sharp-pointed.

Transverse section of leaf blade, physiology. C4; XyMS+. PCR sheath outlines even. PCR sheath extensions present, or absent. Maximum number of extension cells when present, 1. PCR cell chloroplasts centripetal. Mesophyll with radiate chlorenchyma. Leaf blade ‘nodular’ in section. 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; nowhere forming ‘figures’. Sclerenchyma all associated with vascular bundles.

Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae. Soreng et al. (2015): Panicoideae; Panicodae; Paniceae; Panicinae. 7 species.

Distribution, phytogeography, ecology. Australia, Burma.

Mesophytic to xerophytic.

References, etc. Morphological/taxonomic: Lazarides and Webster 1984. Leaf anatomical: studied by us - Y. australiensis (Domin) Lazarides & Webster, Y. majuscula (F. Muell. ex Benth.) Lazarides & Webster, Y. muelleri (Hughes) Lazarides & Webster, Y. nulla Lazarides & Webster Y. pauciflora (R.Br.) Lazarides & Webster.

Illustrations. • Y. australiensis: Gardner, 1952. • Floret and palea, S.E.M. (Y. australiensis and Y. majuscula). • Close-up of opened spikelet of Y. australiensis. Yakirra australiensis. Upper glume pulled down, showing the swollen stipe bearing the small, smooth, indurated L2 within the larger proximal lemma. • Opened spikelet of Y australiensis showing upper floret detail. • Abaxial epidermis of leaf blade of Y. australiensis: this project. • Abaxial epidermis of leaf blade of Y. australiensis: this project. • Y. muelleri, TS leaf blade: this project. • Y. majuscula, TS 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: 11th December 2017.’.