The grass genera of the world
Including Aegicon Adans., Aegilemma Löve, Aegilonearum Löve, Aegilopodes Löve, Chennapyrum Löve, Comopyrum Löve, Cylindropyrum (Jaub. & Spach) Löve, Gastropyrum (Jaub. & Spach) Löve, Kiharapyrum Löve, Orrhopygium Löve, Patropyrum Löve, Perlaria Fabric., Sitopsis (Jaub. & Spach) Löve
Habit, vegetative morphology. Annual; rhizomatous, or caespitose. Culms 15–80 cm high; herbaceous. Culm internodes hollow. Leaves not basally aggregated; auriculate, or non-auriculate. Leaf blades linear to linear-lanceolate; 1.5–10 mm wide; usually flat; without cross venation. Ligule an unfringed membrane; truncate; 0.2–0.8 mm long.
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 (there often being incomplete spikelets at base and tip of the spike).
Inflorescence. Inflorescence a single spike. Rachides hollowed. Spikelets not all embedded. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes with substantial rachides; disarticulating (usually); falling entire (occasionally - e.g. Cylindropyrum), or disarticulating at the joints. Spikelets solitary; not secund; distichous; sessile, or subsessile.
Female-fertile spikelets. Spikelets 5–12 mm long; not noticeably compressed (usually), or compressed laterally; disarticulating above the glumes, or falling with the glumes, or not disarticulating. Rachilla prolonged beyond the uppermost female-fertile floret; hairy; the rachilla extension with incomplete florets. Hairy callus absent. Callus very short; blunt.
Glumes two; more or less equal; shorter than the adjacent lemmas, or long relative to the adjacent lemmas; lateral to the rachis; without conspicuous tufts or rows of hairs; not pointed (usually with one or more teeth or awns); not subulate; awned (sometimes with more than one awn), or awnless; non-carinate (generally rounded on the back); similar (leathery). Lower glume 7–13 nerved. Upper glume 7–13 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. Spikelets without proximal incomplete florets.
Female-fertile florets 2–8. Lemmas one to three toothed, or awned; similar in texture to the glumes to decidedly firmer than the glumes; becoming indurated to not becoming indurated; entire, or incised; awnless, or mucronate, or awned. Awns when present, 1, or 3; median, or median and lateral; the median similar in form to the laterals (when laterals present); from a sinus, or apical; non-geniculate; much shorter than the body of the lemma to much longer than the body of the lemma; entered by one vein. The lateral awns when present, shorter than the median, or about equalling the median. Lemmas hairy, or hairless; non-carinate (dorsally rounded); 5–7 nerved (usually), or 9–13 nerved (Kiharapyrum); with the nerves non-confluent. Palea present; relatively long; apically notched; not indurated (membranous); 2-nerved; 2-keeled. Lodicules present; 2; free; membranous; ciliate; not toothed. Stamens 3. Anthers 1.5–4.5 mm long; not penicillate. Ovary apically hairy; without a conspicuous apical appendage. Stigmas 2.
Fruit, embryo and seedling. Fruit adhering to lemma and/or palea, or free from both lemma and palea; medium sized; longitudinally grooved; compressed dorsiventrally; with hairs confined to a terminal tuft. Hilum long-linear. Embryo large to small (to about 1/3 the caryopsis length); not waisted. Endosperm hard; without lipid; containing only simple starch grains.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally (though the costals rather 270,4 smaller); of similar wall thickness costally and intercostally (thick walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls (e.g. A. cylindrica), or having straight or only gently undulating walls. Microhairs absent. Stomata common; 42–45 microns long. Subsidiaries parallel-sided. Guard-cells overlapped by the interstomatals. Intercostal short-cells common, or absent or very rare; in cork/silica-cell pairs (in A. cylindrica); silicified (in A. cylindrica). Intercostal silica bodies rounded. Crown cells present (abundant costally, in A. cylindrica). Costal short-cells predominantly paired (e.g. in A. cylindrica), or neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies horizontally-elongated crenate/sinuous, or rounded (exclusively, in A. cylindrica), or tall-and-narrow.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade. Leaf blade with distinct, prominent adaxial ribs, or nodular in section (the adaxial ribs wide and low); with the ribs more or less constant in size. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans (or the groups of fairly uniform cells). All the vascular bundles accompanied by sclerenchyma (except the extreme laterals, in A. cylindrica). Combined sclerenchyma girders present, or absent; nowhere forming figures. Sclerenchyma all associated with vascular bundles.
Culm anatomy. Culm internode bundles in one or two rings.
Special diagnostic feature. Plant and inflorescence not as in Lygeum (q.v.).
Cytology. Chromosome base number, x = 7. 2n = 14 and 28, or 42 (rarely). 2, 4, and 6 ploid. Haplomic genome content B, or C, or D, or L, or M, or U, or B and U, or C and D, or C and U, or D and M, or M and U, or D, M, and U. Haploid nuclear DNA content 2.3–7.5 pg (21 species, mean 5.6). Mean diploid 2c DNA value 11.2 pg (11 species, 7.2–14.3).
Classification. Watson & Dallwitz (1994): Pooideae; Triticodae; Triticeae. Soreng et al. (2015): Pooideae; Triticodae; Triticeae; Triticinae. 22 species.
Distribution, phytogeography, ecology. Western Mediterranean to central Asia.
Commonly adventive. Xerophytic; species of open habitats.
Economic aspects. Significant weed species: A. cylindrica, A. geniculata, A. triuncialis. Important native pasture species: several (e.g. A. cylindrica, A. kotschyi, A. triuncialis considered useful).
Hybrids. Intergeneric hybrids with Triticum (×Aegilotriticum Wagner ex Tschermak), Secale (×Aegilosecale Ciferri & Giacom.), Dasypyrum, Elytrigia.
Rusts and smuts. Rusts Puccinia. Taxonomically wide-ranging species: Puccinia graminis, Puccinia striiformis, Puccinia hordei, and Puccinia recondita. Smuts from Tilletiaceae and from Ustilaginaceae. Tilletiaceae Tilletia and Urocystis. Ustilaginaceae Ustilago.
References, etc. Morphological/taxonomic: Löve 1984. Leaf anatomical: Metcalfe 1960; this project.
Illustrations. • A. neglecta, as A. ovata: P. Beauv. (1812). • A. triuncialis (Hitchcock and Chase (1950). • Abaxial epidermis of leaf blade (A. cylindrica)
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: 12th March 2017. delta-intkey.com/grass’.