The grass genera of the world
~ Agropyron; cf.Brachypodium
Habit, vegetative morphology. Perennial; caespitose. Culms 17–60 cm high; herbaceous; unbranched above. Young shoots extravaginal (A. calcis), or intravaginal. Leaves not basally aggregated; auriculate. Sheath margins free. Leaf blades apically flat; narrow; rolled (usually), or flat; without cross venation; persistent. Ligule an unfringed membrane; truncate; short.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets; inbreeding; exposed-cleistogamous, or chasmogamous, or exposed-cleistogamous and chasmogamous.
Inflorescence. Inflorescence few spikeleted to many spikeleted; a single raceme (the spikelets somewhat spreading). Inflorescence with axes ending in spikelets (these often abortive), or axes not ending in spikelets (terminated by a straight or curled, bristlelike appendage in A. uncinatum). Rachides hollowed (notched against the spikelets). Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; not secund; distichous; subsessile to pedicellate (i.e., the spikelets more or less distinctly stalked); imbricate.
Female-fertile spikelets. Spikelets 6–14 mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets.
Glumes present; two; very unequal to more or less equal; shorter than the spikelets; joined (slightly, at the base); lateral to the rachis; hairy (A. calcis), or hairless; when hairless, glabrous; pointed; not subulate; awnless; non-carinate; similar (rigid, broadly lanceolate, rather asymmetric). Lower glume 4–6 nerved. Upper glume (3–)5–7 nerved (sic: glumes not 3 nerved). Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped.
Female-fertile florets 5–7. Lemmas slightly involute; similar in texture to the glumes; not becoming indurated; entire; pointed; awned. Awns 1; median; apical; hooked (in A. uncinatum), or not hooked; non-geniculate; much shorter than the body of the lemma to about as long as the body of the lemma. Lemmas carinate to non-carinate; without a germination flap; 5 nerved, or 7 nerved, or 10–14 nerved (A. uncinatum); with the nerves confluent towards the tip. Palea present; relatively long; apically notched; awnless, without apical setae; 2-nerved; 2-keeled. Lodicules present; 2; ciliate, or glabrous. Stamens 3. Anthers 2–4 mm long (sic); not penicillate. Ovary apically apically hairy. Styles free to their bases. Stigmas 2; white.
Fruit, embryo and seedling. Fruit adhering to lemma and/or palea, or free from both lemma and palea; small (3–4 mm long). Hilum long-linear. Embryo small.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally (the costals smaller); of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular (a few almost fusiform in A. pectinatum); having markedly sinuous walls (exaggeratedly so in A. velutinum). Microhairs absent. Stomata common; 33–39 microns long (in A. retrofractum and A. velutinum), or 40.5–42 microns long (in A. pectinatum). Subsidiaries parallel-sided, or parallel-sided and dome-shaped, or parallel-sided, dome-shaped, and triangular (in A. velutinum); including both triangular and parallel-sided forms on the same leaf (and domes, in A. velutinum), or not including both parallel-sided and triangular forms on the same leaf. Guard-cells overlapped by the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs; silicified. Prickles and macrohairs often common. Crown cells present, or absent. Costal short-cells predominantly paired. Costal silica bodies rounded (plus many irregularly isodiametric forms).
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade; traversed by columns of colourless mesophyll cells. Leaf blade with distinct, prominent adaxial ribs; with the ribs more or less constant in size (round topped). Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups to not present in discrete, regular adaxial groups (scarcely developed bulliform groups only, in some of the furrows); in groups of fairly evenly sized cells. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the bundles); forming figures (most bundles with Is). Sclerenchyma all associated with vascular bundles.
Cytology. Chromosome base number, x = 7. 2n = 14. 2 ploid. Haplomic genome content W.
Classification. Watson & Dallwitz (1994): Pooideae; Triticodae; Triticeae. Soreng et al. (2015): Pooideae; Triticodae; Triticeae; Hordeinae. 5 species.
Distribution, phytogeography, ecology. Australia, New Zealand and New Guinea.
References, etc. Morphological/taxonomic: Löve 1984. Leaf anatomical: this project.
Illustrations. • A. pectinatum, as Festuca pectinata: Labillardière, Nov. Holl. Pl. spec. 1 (1804). • Spikelet of A. pectinatum. • Floret of A. pectinatum
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’.