Periballia Trin.
From the Greek peri (around) and ballo (to throw), allusion obscure.
Including Molineria Parl., Molineriella Rouy
Sometimes referred to Deschampsia
Habit, vegetative morphology. Annual; caespitose (or the culms solitary). Culms 3–25 cm high; herbaceous. Culm nodes glabrous. Leaves vestigially auriculate, or non-auriculate. Leaf blades linear; narrow; 0.5–2 mm wide; setaceous, or not setaceous; flat, or rolled (convolute); without cross venation; persistent; an unfringed membrane.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate (the lower branches sterile in P. involucrata); open; without conspicuously divaricate branchlets; with capillary branchlets. 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 1.75–2 mm long; compressed laterally; disarticulating above the glumes; with distinctly elongated rachilla internodes between the florets. Rachilla terminated by a female-fertile floret; hairy, or hairless. Hairy callus present (the hairs 1/5–2/3 the lemma length).
Glumes two; more or less equal; shorter than the spikelets; shorter than the adjacent lemmas; free; awnless; similar (membranous). Lower glume 1–3 nerved. Upper glume 1–3 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.
Female-fertile florets 2. Lemmas lanceolate; less firm than the glumes (hyaline), or similar in texture to the glumes; not becoming indurated; entire to incised; not deeply cleft (blunt, truncate or irregularly toothed); awnless, or awned. Awns if present, 1; median; dorsal; from near the top to from well down the back; non-geniculate; straight. Lemmas hairless; non-carinate; 3–7 nerved. Palea present; tightly clasped by the lemma; 2-nerved. Lodicules present; 2; free; membranous; glabrous; not toothed. Stamens 3. Anthers 0.8–1.2 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; narrowly ellipsoid; longitudinally grooved (or flattened, on one face). Hilum short. Embryo small; not waisted. Endosperm liquid in the mature fruit; without lipid.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (the costals very narrow, parallel-sided); differing markedly in wall thickness costally and intercostally (the costals thicker-walled). Mid-intercostal long-cells fusiform; having straight or only gently undulating walls (the walls thin). Microhairs absent. Stomata common. Subsidiaries parallel-sided. Guard-cells overlapped by the interstomatals. Intercostal short-cells absent or very rare. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies horizontally-elongated crenate/sinuous, or horizontally-elongated smooth; not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+.
Cytology. Chromosome base number, x = 4 and 7. 2n = 8, 14, and 18. 2 ploid. Chromosomes ‘large’. Haploid nuclear DNA content 3.3 pg (1 species). Mean diploid 2c DNA value 6.6 pg (P. involucrata).
Taxonomy. Pooideae; Poodae; Aveneae.
Distribution, ecology, phytogeography. 3 species; Mediterranean. Commonly adventive. Xerophytic; species of open habitats. Dry sandy places.
Holarctic. Boreal and Tethyan. Euro-Siberian. Mediterranean. European.
References, etc. Leaf anatomical: this project.
Special comments. Anatomical data largely epidermal only.
Illustrations. • Inflorescence. • Inflorescence detail. • Spikelets
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).
