The grass genera of the world
~ Agrostis, Oryzopsis
Habit, vegetative morphology. Perennial; densely caespitose (from a short, cataphyllous rhizome). Culms 70–150 cm high; herbaceous; unbranched above. Culm nodes glabrous. Young shoots intravaginal. Leaves mostly basal; non-auriculate. Leaf blades narrow (up to 8 mm wide, to 40 cm long, stiff); flat, or rolled (flat to involute); without cross venation; persistent. Ligule an unfringed membrane; truncate; 1–1.5 mm long.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate; open (large, lax, the branches in verticils of 5 to 8); with capillary branchlets; espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets 2.75–3.5 mm long; greenish purple to leaden; compressed laterally to not noticeably compressed; disarticulating above the glumes. Rachilla terminated by a female-fertile floret. Hairy callus present (small). Callus short (0.15–0.2 mm); blunt (obtuse, conical, straight).
Glumes two; very unequal to more or less equal (G1 2.5–3 mm, G2 2.75–3.5 mm); exceeding the spikelets; (the upper) long relative to the adjacent lemmas; hairless; glabrous (apart from the scabrous midrib); pointed (or the G2 apically erose); awnless (G2 with the midrib slightly excurrent); carinate; similar (scarious). Lower glume 1 nerved. Upper glume 1 nerved, or 3 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.
Female-fertile florets 1. Lemmas convolute to not convolute (hiding the upper part of the palea); decidedly firmer than the glumes (persistently membranous); not becoming indurated; incised; 2 lobed; not deeply cleft (minutely bilobed at the tip); awned. Awns 1; median; from a sinus (i.e., from between the minute lobes); non-geniculate; straight, or flexuous; entered by several veins (by all three); deciduous. Lemmas hairless; glabrous (to scaberulous); non-carinate (?); having the margins lying flat on the palea; 3 nerved; with the nerves confluent towards the tip. Palea present (only its upper part covered, at anthesis, by the overlapping upper margins of the lemma); relatively long to conspicuous but relatively short (1.5–1.6 mm, compared with the 2–2.25 mm lemma); apically erose to slightly fimbriate; awnless, without apical setae; 2-nerved (weakly so); keel-less (neither keeled nor furrowed). Lodicules present; 2; free (but closely set and imbricate); membranous; glabrous; not toothed (lanceolate lingular); not or scarcely vascularized. Stamens 1. Anthers about 1 mm long (yellow); not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea (exposed between the divergent lemma and palea); small (about 1.5 mm long, brown); fusiform; smooth (finely reticulate). Hilum short (in the lower 1/6 of the grain, elliptic). Embryo large to small (about 0.3 times the grain length); with an epiblast; without a scutellar tail (the primary root bent away from the main axis); with a negligible mesocotyl internode. Embryonic leaf margins meeting.
Abaxial leaf blade epidermis. Costal/intercostal zonation lacking. Papillae absent. Microhairs absent. Stomata absent or very rare. Intercostal short-cells common; in cork/silica-cell pairs. Costal short-cells predominantly paired (with a few threes). Costal silica bodies horizontally-elongated smooth to rounded (more or less circular, irregularly isodiametric, oval to slightly elongated, and irregular).
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma. Leaf blade with distinct, prominent adaxial ribs; with the ribs very irregular in sizes (of two size orders). Midrib conspicuous; with one bundle only. Bulliforms present in discrete, regular adaxial groups (lining the adaxial grooves). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming figures (the major bundles with Ts).
Classification. Watson & Dallwitz (1994): Stipoideae; Stipeae. Soreng et al. (2015): Pooideae; Stipeae. 1 species (A.lessoniana).
Distribution, phytogeography, ecology. New Zealand.
Mesophytic (at the edges of streamlets, up to 460 m).
References, etc. Morphological/taxonomic: Veldkamp 1985. Leaf anatomical: 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: 13th November 2017. delta-intkey.com/grass’.