The grass genera of the world
Type species: Type: A. laguroides R.Br.
Including Gamelythrum Nees, Pentacraspedon Steud.
Habit, vegetative morphology. Perennial; short rhizomatous, or rhizomatous and caespitose, or caespitose. Culms 15–75 cm high; herbaceous; unbranched above. Culm nodes glabrous (and dark). Culm internodes hollow. Young shoots intravaginal. Leaves mostly basal, or not basally aggregated; non-auriculate. Leaf blades narrow; 1–3 mm wide; setaceous, or not setaceous (often acicular); flat, or rolled; without abaxial multicellular glands, or exhibiting multicellular glands abaxially (at the bases of macrohairs); not pseudopetiolate; without cross venation; disarticulating from the sheaths (commonly), or persistent. Ligule a fringe of hairs. Contra-ligule absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant, or all alike in sexuality; hermaphrodite, or hermaphrodite and sterile (sometimes reduced at the base of the inflorescence).
Inflorescence. Inflorescence a single spike (or approaching one), or paniculate; contracted; more or less ovoid, or spicate; espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; sessile to pedicellate; consistently in long-and-short combinations, or not in distinct long-and-short combinations. The shorter spikelets hermaphrodite. The longer spikelets hermaphrodite.
Female-fertile spikelets. Spikelets 3–6 mm long; abaxial; compressed laterally (sometimes, slightly), or not noticeably compressed to compressed dorsiventrally (mostly); disarticulating above the glumes. Rachilla terminated by a female-fertile floret. Hairy callus present. Callus short, or long (short and obtuse, or long and stipitate).
Glumes two; more or less equal; shorter than the adjacent lemmas to long relative to the adjacent lemmas; dorsiventral to the rachis; hairy, or hairless; usually entire, but sometimes lemmalike with three pointed lobes; awned to awnless; non-carinate; similar (acute, obtuse or cleft, membranous or papery). Lower glume 3 nerved. Upper glume 3 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.
Female-fertile florets 1. Lemmas becoming decidedly firmer than the glumes; not becoming indurated; incised; 3 lobed; deeply cleft; awned. Awns 3; median and lateral (by bristles from the tips of the lobes); the median similar in form to the laterals; non-geniculate; hairless to hairy; about as long as the body of the lemma to much longer than the body of the lemma. The lateral awns about equalling the median. Lemmas hairy, or hairless; non-carinate; without a germination flap; 3 nerved. Palea present; relatively long; apically notched to deeply bifid; with apical setae, or awned; textured like the lemma; not indurated (hyaline); 2-nerved; keel-less. Lodicules present; 2; fleshy; glabrous; not or scarcely vascularized. Stamens 3. Anthers 1–5 mm long; not penicillate. Ovary apically glabrous. Styles fused. Stigmas 2.
Fruit, embryo and seedling. Fruit compressed dorsiventrally. Hilum short. Pericarp free (and opaque). Embryo small. Endosperm containing compound starch grains. Embryo without an epiblast; with a scutellar tail; with an elongated mesocotyl internode. Embryonic leaf margins meeting.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous, or lacking (A. laguroides). Papillae present (usually very conspicuous and constituting volcano-like pits, but inconspicuous and in the form of less prominent pits in (e.g.) A. amphipogonoides); intercostal, or costal and intercostal. Intercostal papillae not over-arching the stomata; consisting of one symmetrical projection per cell (sometimes, costally), or several per cell (intercostal long-cells with rows). Long-cells markedly different in shape costally and intercostally; of similar wall thickness costally and intercostally (thick walled). Intercostal zones with typical long-cells (but some rather short). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present (sometimes, but not in the mid-laminar zone), or absent (from all material seen except at the base of the lamina, but common adaxially and on lemmas, etc.); chloridoid-type and Enneapogon-type (having long basal cells and short, thin-walled, easily collapsing ovoid apices which are at least sometimes 2-celled, cf. Enneapogon - and ordinary chloridoid type microhairs seen on the lemmas of A. caricinus); with partitioning membranes (A. strictus). The partitioning membranes in the apical cell. Stomata absent or very rare, or common (A. amphipogonoides); (31.5–)33–42 microns long. Subsidiaries non-papillate; dome-shaped, or dome-shaped and triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs, or not paired (solitary); silicified. Intercostal silica bodies absent, or present and perfectly developed. Costal short-cells neither distinctly grouped into long rows nor predominantly paired (all solitary). Costal silica bodies present and well developed, or poorly developed to absent (mostly); present throughout the costal zones; (these or at least the silica-cells) tall-and-narrow (almost exclusively, in all the species examined), or rounded (a few, notably in A. strictus), or saddle shaped (few at most).
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C3; XyMS+. Mesophyll with radiate chlorenchyma; Isachne-type (almost!), or not Isachne-type. Leaf blade with distinct, prominent adaxial ribs; with the ribs very irregular in sizes. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups (but the outer walls unusually thick), or not present in discrete, regular adaxial groups; when present, in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (e.g A. avenaceus), or absent; when present, forming figures (i.e. in A. avenaceus). Sclerenchyma all associated with vascular bundles, or not all bundle-associated (abaxial, continuous or interrupted). The extra sclerenchyma when present, in abaxial groups to in a continuous abaxial layer. The lamina margins with fibres.
Classification. Watson & Dallwitz (1994): Arundinoideae (?); Amphipogoneae. Soreng et al. (2015): Arundinoideae; Arundineae. 8 species.
Distribution, phytogeography, ecology. Australia.
Xerophytic; species of open habitats. Dry sandy grassland.
Rusts and smuts. Smuts from Ustilaginaceae. Ustilaginaceae Ustilago.
References, etc. Morphological/taxonomic: Vickery 1950. Leaf anatomical: studied by us - A. amphipogonoides (Steud) Vickery, A. avenaceus R. Br., A. caricinus F. Muell., A. debilis R. Br., A. laguroides R. Br., A. strictus R. Br., A. turbinatus R. Br.
Special comments. Subfamilial relationships very problematical - the spikelet form (especially the lemma) and the microhairs are reminiscent of Enneapogon. Illustrations. • A. debilis, A. laguroides, A. strictus: Gardner, 1952. • A. amphipogonoides, A. turbinatus: Gardner, 1952. • A. strictus, abaxial epidermis of leaf blade: this project. • A. caricinus, abaxial epidermis of leaf blade: this project. • ‘Enneapogon-type’ microhairs of Amphipogon strictus and Enneapogon nigricans: longitudinal EM sections (Amarasinghe)
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. delta-intkey.com/grass’.