| # The grass genera of the world |

L. Watson, T.D. Macfarlane, and M.J. Dallwitz

### Periballia Trin.

From the Greek peri (around) and ballo (to throw), allusion obscure.

~ Deschampsia

Type species: Type: P. hispanica Trin., nom. illeg..

Including Molineria Parl., Molineriella Rouy

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; apically cucullate; narrow; 0.5–2 mm wide; setaceous, or not setaceous; flat, or rolled (convolute); without cross venation; persistent. Ligule an unfringed membrane.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.

Inflorescence. Inflorescence paniculate (the lower branches sterile in P. involucrata); open; 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 apically 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).

Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Aveneae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Airinae. 3 species.

Distribution, phytogeography, ecology. Mediterranean.

Commonly adventive. Xerophytic; species of open habitats. Dry sandy places.

References, etc. Leaf anatomical: studied by us - P. minuta (L.) Aesch. & Graebn.

Special comments. Anatomical data largely epidermal only.

Illustrations. • Periballia involucrata: Trinius, Spec. Graminum 3 (1830). • Inflorescence of Periballia minuta. • Inflorescence detail (Periballia minuta). • Spikelets of Periballia minuta.

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: 15th June 2025. delta-intkey.com’.

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