The grass genera of the world
Type species: Type: G. fragilis (L.) P.Beauv.
Including Arthrostachya Link, Falmiria Reichenb., Cyclichnium Dulac, Meringurus Murbeck
Habit, vegetative morphology. Biennial or annual; caespitose. Culms 15–120 cm high; herbaceous. Culm nodes glabrous. Culm internodes hollow. Leaves not basally aggregated; non-auriculate. Leaf blades linear; apically cucullate; narrow; 1.5–4 mm wide; flat; without cross venation; persistent. Ligule an unfringed membrane; truncate (minutely serrated); 0.5–0.9 mm long.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence a single spike. Rachides hollowed. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes disarticulating, or persistent (variable); when disarticulating, disarticulating at the joints (above the insertions of the spikelets). Spikelets solitary (appressed to the concave rachis); not secund; distichous; sessile.
Female-fertile spikelets. Spikelets 5.5–20 mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairless; the rachilla extension with incomplete florets. Hairy callus absent. Callus short; blunt.
Glumes two; very unequal to more or less equal; shorter than the spikelets to about equalling the spikelets; (the longer) long relative to the adjacent lemmas; lateral to the rachis; pointed; awnless; non-carinate; similar. Lower glume 3–5 nerved. Upper glume 5–11 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped.
Female-fertile florets 3–11. Lemmas similar in texture to the glumes (leathery); not becoming indurated; entire to incised (or bicuspid); awned, or awnless (G. hispanica). Awns 1; median; dorsal; from near the top; geniculate; entered by one vein. Lemmas hairy, or hairless; weakly carinate; 5 nerved, or 7 nerved, or 9 nerved. Palea present; relatively long; entire to apically notched; awnless, without apical setae; 2-nerved. Lodicules present; 2; free; membranous; glabrous; toothed. Stamens 3. Anthers 2.5–6 mm long; not penicillate. Ovary apically hairy. Styles free to their bases. Stigmas 2; white.
Fruit, embryo and seedling. Fruit with hairs confined to a terminal tuft. Hilum short (round). Embryo small. Endosperm liquid in the mature fruit; with lipid; containing compound starch grains.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally. Mid-intercostal long-cells fusiform; having straight or only gently undulating walls. Microhairs absent. Stomata absent or very rare (G. fragilis), or common; in G. maroccana, 28–33 microns long. Subsidiaries parallel-sided. Guard-cells overlapped by the interstomatals. Intercostal short-cells absent or very rare; in cork/silica-cell pairs, or not paired; silicified, or not silicified. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies horizontally-elongated crenate/sinuous, or horizontally-elongated smooth.
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; with the ribs more or less constant in size. Midrib conspicuous (rarely), or not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups (between the bundles); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders absent. Sclerenchyma all associated with vascular bundles.
Cytology. Chromosome base number, x = 7. 2n = 14 (and 14+1). 2 ploid. Chromosomes large.
Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Aveneae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Aveninae. 4 species.
Distribution, phytogeography, ecology. Mediterranean, Azores.
Commonly adventive. Mesophytic to xerophytic; species of open habitats; glycophytic. Weedy places.
Rusts and smuts. Rusts Puccinia. Taxonomically wide-ranging species: Puccinia striiformis, Puccinia hordei, and Puccinia recondita. Smuts from Tilletiaceae. Tilletiaceae Entyloma.
References, etc. Leaf anatomical: this project.
Illustrations. • G. fragilis, as G. avenacea: P. Beauv. (1812). • G. fragilis: Lamson-Scribner (1890). • Inflorescence detail (G. fragilis). • Inflorescence detail (G. fragilis). • Ligule of G. fragilis. • G. fragilis, TS leaf blade: this project. • G. coarctata, as Avena geminiflora: Kunth (1835)
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’.