The grass genera of the world
Type species: Type: A. mollis (R.Br.) S.W.L.Jacobs & J.Everett.
Habit, vegetative morphology. Perennial; caespitose (mostly), or rhizomatous and caespitose (and two shrubby species - subgenus Bambusina). Culms 10–250 cm high; woody and persistent (subgenus Bambusina, with persistent, bamboo-like canes), or herbaceous; branched above, or unbranched above. Culm nodes hairy, or glabrous. Culm internodes solid (rarely), or hollow. Young shoots intravaginal (mostly), or extravaginal, or extravaginal and intravaginal. Leaves mostly basal, or not basally aggregated; auriculate, or non-auriculate. Leaf blades greatly reduced (occasionally), or not all greatly reduced (usually); linear; narrow; over 0.5 mm wide; setaceous, or not setaceous; flat, or folded, or rolled (then involute or convolute), or acicular; not pseudopetiolate; without cross venation; persistent; rolled in bud, or once-folded in bud. Ligule an unfringed membrane, or a fringed membrane. Contra-ligule present, or absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets; inbreeding; exposed-cleistogamous, or chasmogamous; without hidden cleistogenes.
Inflorescence. Inflorescence few spikeleted to many spikeleted; paniculate; not deciduous; open, or contracted; with conspicuously divaricate branchlets (e.g. A. elegantissima), or without conspicuously divaricate branchlets; without capillary branchlets; espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets 3–20 mm long; fusiform (narrow); compressed laterally to not noticeably compressed (mostly, more or less terete), or compressed dorsiventrally (sometimes, slightly); disarticulating above the glumes. Rachilla terminated by a female-fertile floret. Hairy callus present (oblique). The callus hairs white, or brown (or orange), or purple. Callus short (rarely), or long (mostly); pointed (usually), or blunt (rarely).
Glumes present; two; very unequal to more or less equal; about equalling the spikelets to exceeding the spikelets (usually exceeding them); long relative to the adjacent lemmas; usually pointed; awnless; carinate to non-carinate; similar (linear or lanceolate, membranous or papery, often acute or acuminate, rarely muticous or mucronate). Lower glume 1–5(–6) nerved. Upper glume (1–)3–7 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.
Female-fertile florets 1. Lemmas convolute (nearly always, at least partially concealing the palea), or not convolute (in only two species); saccate (conspicuously so, in A. gibbosa), or not saccate (nearly always); without a crown; decidedly firmer than the glumes; with round or oval abaxial epidermal silica bodies; becoming indurated (usually, horny); white in fruit, or yellow in fruit, or brown in fruit, or black in fruit (or purple); entire (usually), or incised; when incised, inconspicuously 1–2 lobed; not deeply cleft; awned. Awns not of the triple/trifid, basal column type; 1; nearly always median (but acentric on the gibbous floret of A. gibbosa); from a sinus (rarely, inconspicuously), or apical; geniculate (or sometimes bi-geniculate), or non-geniculate; when non-geniculate, flexuous; hairless, or hairy (or scabrous, but not plumose); much shorter than the body of the lemma to much longer than the body of the lemma (14–200 mm long); entered by several veins (3); persistent (although articulated at the base of the column, and easily breaking off there). Awn bases twisted. Lemmas hairy (usually, the hairs often brownish), or hairless (rarely); non-carinate (terete); having the margins inrolled against the palea (when involute - i.e. rarely,), or having the margins lying flat on the palea (nearly always, but convolute); without a germination flap; 3–5(–7) nerved. Palea usually present (usually hidden by the lemma); relatively long (nearly always, usually slightly shorter than the lemma, sometimes slightly exceeding it), or conspicuous but relatively short (sometimes only about a third of the lemma length in A. ramosissima and A. verticillata, even shorter in A. tuckeri); tightly clasped by the lemma; not prow-tipped; entire (usually blunt or acute, ocasionally acuminate); awnless, without apical setae; thinner than the lemma (usually translucent to leathery in the median strip, with membranous margins); not indurated; 2-nerved (even when small); keel-less (mostly), or 2-keeled (sometimes depressed between the nerves). Palea back scabrous, or hairy. Lodicules present; 2, or 3; free; membranous (stipoid, the third member when present usually more or less different); glabrous; not toothed. Stamens 3. Anthers 1.2–9 mm long; penicillate (often), or not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2; white.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small, or medium sized, or large; fusiform; not grooved; compressed laterally, or not noticeably compressed. Hilum long-linear. Embryo small; not waisted. Endosperm hard; without lipid; containing only simple starch grains, or containing compound starch grains. Embryo with an epiblast; without a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins meeting.
Seedling with a short mesocotyl, or with a long mesocotyl. First seedling leaf with a well-developed lamina. The lamina narrow; erect; 3–5 veined.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous (in 10 of the eleven species examined), or lacking (A. teretifolia). Papillae present (A. densiflora, A. falcata, A. nervosa), or absent (A. aristiglumis, A. bigeniculata, A. blackii, A. elegantissima, A. pubescens, A. ramosissima, A. teretifolai, A. verticillata); intercostal (and sometimes on cells bordering the costae). Intercostal papillae not over-arching the stomata; several per cell (about 5–20 per long-cell, in a median or sometimes partially double row along the cells, circular or sometimes more or less branched, sometimes (e.g. A. densiflora) clearly of the coronate-pit type, cf. Poa helmsii). Long-cells similar in shape costally and intercostally, or markedly different in shape costally and intercostally (the costals often much narrower, as well as smaller); of similar wall thickness costally and intercostally, or differing markedly in wall thickness costally and intercostally (the walls quite thin to thick, the costals often somewhat thicker walled). Intercostal zones with typical long-cells (nearly always), or with typical long-cells and exhibiting many atypical long-cells (A. densiflora having many isodiametric in some zones). Mid-intercostal long-cells rectangular, or rectangular and fusiform (some obvious fusiforms in A. ramosissima and A. verticillata); having markedly sinuous walls, or having markedly sinuous walls and having straight or only gently undulating walls (e.g. A. densiflora, A. elegantissima, A. verticillata), or having straight or only gently undulating walls (A. ramosissima). Microhairs present (probably, sometimes - but very scarce, found to date only adaxially), or absent; elongated; ostensibly one-celled; hard to find and study, seemingly peculiar - thin-walled, perhaps one-celled: see photos in Johnston and Watson 1976. Stomata common (A. aristiglumis, A. bigeniculata, A. verticillata), or absent or very rare (few in the material seen of A. falcata, none seen in A. blackii, A. densiflora, A. elegantissima, A. nervosa, A. pubescens, A. ramosissima, A. teretifolia); when present, (22–)24–45(–48) microns long. Subsidiaries non-papillate; low to fairly high dome-shaped (to almost parallel in A. aristiglumis). Guard-cells overlapping to flush with the interstomatals (more or less flush). Intercostal short-cells common, or absent or very rare (only A. verticillata); not paired (usually), or in cork/silica-cell pairs and not paired (sometimes some ostensibly solitary, and some short rows in A. nervosa); silicified (usually), or not silicified (mostly, in A. elegantissima). Intercostal silica bodies absent (rarely), or imperfectly developed to present and perfectly developed; rounded, crescentic, and tall-and-narrow (commonly one or more of these, usually with intermediates, the rounded forms usually somewhat vertically elongated), or cubical (a few, e.g. in A. aristiglumis), or cross-shaped (some, in A. ramosissima). Commonly with thick or thin walled prickles costally, or intercostally or both, occasionally large thick walled macrohairs, neither prickles no macrohairs seen in A. aristiglumis, A. bigeniculata, A. pubescens, A. teretifolia. Costal short-cells predominantly conspicuously in long rows (usually, but in some species the rows interrupted by relatively long short-cells), or predominantly paired (sometimes predominating everywhere or almost everywhere, e.g. A. pubescens, A. teretifolia), or conspicuously in long rows and predominantly paired (varying from file to file, e.g. A. bigeniculata, A. blackii), or predominantly paired and neither distinctly grouped into long rows nor predominantly paired (A. pubescens, exhibiting many files with pairs and short rows). Costal silica bodies present and well developed (usually), or present and well developed and poorly developed (e.g. A. falcata, with many imperfect); present throughout the costal zones (A. densiflora, A. pubescens, A. teretifolia), or present in alternate cell files of the costal zones (A. aristiglumis), or present throughout the costal zones and present in alternate cell files of the costal zones (the costae varying, A. bigeniculata, A. blackii, A. falcata), or confined to the outer files of the costal zones and present in alternate cell files of the costal zones (A. nervosa, depending on the zone examined), or present in alternate cell files of the costal zones (A. aristiglumis, A. ramosissima, A. verticillata); panicoid-type (unambiguously, and predominating everywhere in A, aristiglumis, A. elegantissima, A. nervosa, A. ramosissima, A. verticillata), or rounded and panicoid-type (with intermediates, A. bigeniculata), or horizontally-elongated smooth, rounded, and panicoid-type (with intermediates, in A. falcata and A. pubescens), or horizontally-elongated crenate/sinuous and panicoid-type (in A. blackii and A. densiflora, the pooid forms short with no more than two or three crenations per side), or rounded and tall-and-narrow (usually more or less vertically elongated, A. teretifolia); when panicoid type, cross shaped and dumb-bell shaped, or dumb-bell shaped (commonly, but often more or less ambiguously so even when the silica cells are clearly dumb-bell shaped), or dumb-bell shaped to nodular (large in A. ramosissima, A. verticillata); sharp-pointed (a few of the dumb-bells of A. elegantissima being distinctly angular), or not sharp-pointed (usually).
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma, or with radiate chlorenchyma to with non-radiate chlorenchyma (the chlorenchyma usually closely packed, perhaps spongy in A. blackii, A. teretifolia and A. verticillata); without adaxial palisade (but some species exhibit a rather clear abaxial palisade, e.g. A. falcata, A. nervosa, A. teretifolia). Leaf blade with distinct, prominent adaxial ribs (mostly), or with distinct, prominent adaxial ribs to nodular in section (A. elegantissima, A. ramosissima), or nodular in section (A. verticillata); with the ribs very irregular in sizes (more or less alternating large and small, in ten of the twelve species examined), or with the ribs more or less constant in size (A. elegantissima, A. ramosissima). Midrib not readily distinguishable (except positionally); with one bundle only. The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups (in all but one of the species examined), or not present in discrete, regular adaxial groups (perhaps, in A. verticillata); in simple fans (these fairly to very conspicuous, especially large in A. ramosissima). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (at least in all the larger ribs); forming figures (Is, usually fairly massive, with all the main bundles). Sclerenchyma all associated with vascular bundles (in ten of the twelve species examined), or not all bundle-associated (in A. pubescens and A. teretifolia). The extra sclerenchyma in a continuous abaxial layer (A. teretifolia), or in abaxial groups and in a continuous abaxial layer (varying from place to place, in A. pubescens). The lamina margins with fibres.
Phytochemistry. Tissues of the culm bases with abundant starch.
Special diagnostic feature. The upper part of the lemma without pappus-like hairs.
Cytology. Chromosome base number, x = 9, 10, 11, 12, and 22 (?). 2n = 22, 28, 40, 44, 48, 68, and 96 (?). 2, 4, and 8 ploid (? and aneuploids).
Classification. Watson & Dallwitz (1994): Stipoideae; Stipeae. Soreng et al. (2015): Pooideae; Stipeae. About 70 species.
Distribution, phytogeography, ecology. Australia.
Australian and Antarctic.
Commonly adventive. Mesophytic to xerophytic.
Rusts and smuts. Rusts Puccinia. Smuts from Tilletiaceae and from Ustilaginaceae.
References, etc. Morphological/taxonomic: Barkworth 1983; Vickery Jacobs and Everett 1986; Barkworth and Everett 1987; Jacobs and Everett 1996. Leaf anatomical: mainly this project.
Special comments. This is a currently unsatisfactory description of a Stipa segregate. See further comment under Stipa sensu lato. Illustrations. • A. setacea: Hooker, Fl. Tasmaniae (1860). • A. stipoides (as Dichelachne): Hooker, Fl. Novae-Zelandiae (1853). • A. elegantissima: Gardner, 1952. • A. juncifolia, A. aff. nitida: Gardner, 1952. • A. hemipogon: Gardner, 1952. • Leaf form (A. falcata). Austrostipa falcata. Sheath hairy at the auricle positions. • Disarticulated spikelet (A. bigeniculata). • Lemma showing awn attachment. • Spikelet close-up. • Germinating A. falcata: this project. Austrostipa falcata. Emerging radicle (lower left) and shoot (upper right). Austrostipa falcata. Lemma splitting over the embryo. • A. bigeniculata, abaxial epidermis of leaf blade: this project. • A. bigeniculata, abaxial epidermis of leaf blade: this project. • A. bigeniculata, abaxial epidermis of leaf blade: this project. • A. bigeniculata, TS of leaf blade: this project. • A. elegantissima, abaxial epidermis of leaf blade: this project. • A. densiflora, abaxial epidermis of leaf blade: this project. • A. densiflora, TS of leaf blade: this project. • A. teretifolia, abaxial epidermis of leaf blade: this project. • A. blackii, abaxial epidermis of leaf blade: this project. • A. falcata, abaxial epidermis of leaf blade: this project. • A. falcata, TS of leaf blade: this project. • A. pubescens, abaxial epidermis of leaf blade: this project. • A. pubescens, TS of leaf blade: this project. • A. pubescens, TS of leaf blade: this project. • Pollen antigens: Watson and Knox (1976)
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: 13th November 2017. delta-intkey.com/grass’.