The grass genera of the world
The grass genera of the world | |
Yakirra: aboriginal name for some of the species.
Sometimes referred to Ichnanthus australiensis and relatives
Habit, vegetative morphology. Annual, or perennial; caespitose. Culms 8–75 cm high; herbaceous; branched above, or unbranched above. Culm nodes hairy, or glabrous. 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, 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 with axes ending in spikelets. 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 two; very unequal; (the upper) long relative to the adjacent lemmas; hairless (glabrous, save for adaxial hairs at the apex of G2); 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. Palea present; relatively long; entire; awnless, without apical setae; indurated; 2-nerved. Lodicules present; 2; fleshy; glabrous. Stamens 3. Ovary 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.
Special diagnostic feature. Plants not as in Dichanthelium (q.v.).
Taxonomy. Panicoideae; Panicodae; Paniceae.
Distribution, ecology, phytogeography. 7 species; Australia, Burma. Mesophytic to xerophytic.
Paleotropical and Australian. Indomalesian. Indo-Chinese. North and East Australian and Central Australian. Tropical North and East Australian.
References, etc. Morphological/taxonomic: Lazarides and Webster 1984. Leaf anatomical: this project.
Illustrations. • General aspect, spikelet (Y. australiensis). • Floret and palea, S.E.M. (Y. australiensis and Y. majuscula). • Close-up of opened spikelet (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 showing upper floret detail (Y. australiensis). • Abaxial epidermis of leaf blade (Y. australiensis). • Abaxial epidermis of leaf blade (Y. australiensis). • Transverse section of leaf blade (Y. muelleri). • Transverse section of leaf blade (Y. majuscula)
This description is offered for casual browsing only. We strongly advise against extracting comparative information from it. This is much more easily achieved using 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 specified attributes, summaries of attributes within groups of taxa, geographical distribution, classification, and species sampled for anatomy.
Cite this publication as: ‘Watson, L., 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 February 2012. http://delta-intkey.com’.
