Gastridium P. Beauv.
Diminutive of the Greek gaster (belly) referring to the basally swollen glumes.
Habit, vegetative morphology. Annual; caespitose (or the culms solitary). Culms 10–60 cm high; herbaceous. Culm nodes glabrous. Culm internodes hollow. Leaves not basally aggregated; vestigially auriculate, or non-auriculate. Leaf blades linear; narrow; 1.5–4 mm wide; flat; without cross venation; persistent; an unfringed membrane; not truncate (veined); 4–6 mm long.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate; contracted; spicate. Primary inflorescence branches borne distichously. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets 3–6.5 mm long; compressed laterally; disarticulating above the glumes. Rachilla shortly prolonged beyond the uppermost female-fertile floret (or rarely not prolonged?); the rachilla extension when present, naked. Hairy callus absent. Callus short; blunt.
Glumes two; relatively large; very unequal to more or less equal (the lower somewhat longer); exceeding the spikelets; long relative to the adjacent lemmas (the floret enclosed by their swollen bases); conspicuously ventricose; pointed (acuminate); awnless; carinate; similar (swollen, globular and more or less cartilaginous at the base, membranous above). Lower glume 1 nerved. Upper glume 1 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.
Female-fertile florets 1. Lemmas less firm than the glumes; not becoming indurated; incised (more or less dentate); mucronate to awned (the midvein usually excurrent). Awns when present, 1; dorsal; from near the top; geniculate; much shorter than the body of the lemma to much longer than the body of the lemma; entered by one vein. Lemmas hairy, or hairless; non-carinate; 5 nerved. Palea present; relatively long; apically notched; awnless, without apical setae; not indurated (hyaline); 2-nerved; 2-keeled. Lodicules present; 2; free; membranous; glabrous; not toothed. Stamens 3. Anthers 0.5–0.7 mm long; not penicillate. Ovary glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit slightly adhering to lemma and/or palea; small; compressed dorsiventrally (slightly). Hilum short. Embryo small; not waisted. Endosperm hard; with lipid. Embryo with an epiblast; without a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins meeting.
Seedling with a short mesocotyl. First seedling leaf with a well-developed lamina. The lamina narrow; erect; 3 veined.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally (the costals shorter); of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having straight or only gently undulating walls. Microhairs absent. Stomata common; 36–54 microns long. Subsidiaries parallel-sided. Guard-cells overlapped by the interstomatals. Intercostal short-cells absent or very rare; when present, not paired (solitary); silicified. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies horizontally-elongated crenate/sinuous.
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 not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups (in the furrows); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’. Sclerenchyma all associated with vascular bundles.
Cytology. Chromosome base number, x = 7. 2n = 28. 2 ploid. Chromosomes ‘large’.
Taxonomy. Pooideae; Poodae; Aveneae.
Distribution, ecology, phytogeography. 2 species; Canaries, western Europe, Mediterranean. Commonly adventive. Mesophytic to xerophytic; species of open habitats. Grassy places and arable land.
Holarctic and Paleotropical. Boreal, Tethyan, and Madrean. African. Euro-Siberian. Macaronesian and Irano-Turanian. Saharo-Sindian and Sudano-Angolan. European. Sahelo-Sudanian and Somalo-Ethiopian.
References, etc. Leaf anatomical: this project.
Illustrations. • General aspect, spikelet. • General aspect. • Spikelets. Gastridium ventricosum. Basally ventricose glumes.
Cite this publication as: Watson, L., and Dallwitz, M. J. (1992 onwards). ‘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.’ http://biodiversity.uno.edu/delta/. Version: 18th August 1999. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993 onwards, 1998), and Watson and Dallwitz (1994), and Watson, Dallwitz, and Johnston (1986) should also be cited (see References).
