| # The grass genera of the world |

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

### Lolium L.

Latin Lolium: name given by Virgil to a troublesome weed.

Ryegrasses.

Type species: Type: L. perenne L.

Including Arthrochortus Lowe, Craepalia Schrank, Crypturus Link

Habit, vegetative morphology. Annual, or perennial; rhizomatous, or stoloniferous, or caespitose, or decumbent. Culms 10–130 cm high; herbaceous; unbranched above. Culm nodes glabrous. Culm internodes hollow. Leaves not basally aggregated; auriculate. Leaf blades linear; apically cucullate, or apically flat; usually narrow; 2–12 mm wide; flat, or folded, or rolled; not pseudopetiolate; without cross venation; persistent; rolled in bud, or once-folded in bud. Ligule an unfringed membrane; truncate; 0.8–2 mm long.

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

Inflorescence. Inflorescence a single spike (with partially embedded spikelets). Rachides hollowed. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; not secund; conspicuously distichous; sessile.

Female-fertile spikelets. Spikelets 7–26 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.

Glumes one per spikelet (except that the terminal spikelet has two); shorter than the adjacent lemmas, or long relative to the adjacent lemmas; dorsiventral to the rachis; pointed, or not pointed; awnless; non-carinate. Upper glume (i.e. the only glume) 3–7 nerved (membranous). Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped.

Female-fertile florets 2–22. Lemmas less firm than the glumes to decidedly firmer than the glumes (membranous to papery, sometimes turgid or hardening in fruit); becoming indurated to not becoming indurated; entire, or incised; when entire pointed, or blunt; awnless, or awned. Awns when present, 1; from a sinus, or dorsal; when dorsal, from near the top; non-geniculate; hairless; much shorter than the body of the lemma; entered by one vein. Lemmas hairless; non-carinate; 5–7 nerved. Palea present; relatively long (usually ciliate); apically notched; awnless, without apical setae; not indurated; 2-nerved; 2-keeled. Lodicules present; 2; free; membranous; glabrous; toothed, or not toothed; not or scarcely vascularized. Stamens 3. Anthers 1.3–4.5 mm long; not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2; white.

Fruit, embryo and seedling. Fruit somewhat adhering to lemma and/or palea; small, or medium sized, or large; longitudinally grooved; compressed dorsiventrally. Hilum long-linear. Embryo small; not waisted. Endosperm hard; without lipid; containing compound starch grains. Embryo with an epiblast; without a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins meeting.

Seedling with a short mesocotyl, or with a long mesocotyl; with a tight coleoptile. First seedling leaf with a well-developed lamina. The lamina narrow; erect; 3–7 veined.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (costals rectangular, intercostals longer, fusiform); of similar wall thickness costally and intercostally (but the walls of the costals sinuous). Mid-intercostal long-cells fusiform; having straight or only gently undulating walls (those bordering the veins sinuous, by contrast). Microhairs absent. Stomata common. Subsidiaries low dome-shaped, or parallel-sided. Guard-cells overlapped by the interstomatals. Intercostal short-cells absent or very rare. Costal short-cells predominantly paired, or neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies horizontally-elongated crenate/sinuous, or horizontally-elongated smooth, or rounded (some almost cubical); not sharp-pointed.

Transverse section of leaf blade, physiology. C3; XyMS+. PBS cells without a suberised lamella. Mesophyll with non-radiate chlorenchyma. Leaf blade with distinct, prominent adaxial ribs; with the ribs more or less constant in size. Midrib conspicuous; with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present, or absent; nowhere forming ‘figures’. Sclerenchyma all associated with vascular bundles.

Phytochemistry. Tissues of the culm bases with little or no starch. Fructosans predominantly short-chain. Leaves without flavonoid sulphates (1 species).

Cytology. Chromosome base number, x = 7. 2n = 14 and 28. 2 and 4 ploid. Chromosomes ‘large’. Haploid nuclear DNA content (2.2–)3.2–6.9 pg (8 species, mean 5.0). Mean diploid 2c DNA value 9.9 pg (5 species, (4.3-)6.4–13.6).

Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Poeae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Loliinae. 8 species.

Distribution, phytogeography, ecology. Temperate Eurasia, north Africa.

Commonly adventive. Mesophytic; species of open habitats.

Economic aspects. Significant weed species: L. multiflorum, L. perenne, L. persicum, L. remotum, L. rigidum, L. temulentum (darnel - with toxic grain). Cultivated fodder: L. multiflorum, L. perenne. Lawns and/or playing fields: L. perenne.

Hybrids. Intergeneric hybrids with Festuca - ×Festulolium Aschers. & Graebn. (several species of each genus involved).

Rusts and smuts. Rusts — Puccinia. Taxonomically wide-ranging species: Puccinia graminis, Puccinia coronata, Puccinia striiformis, Puccinia brachypodii, Puccinia hordei, and Puccinia recondita. Smuts from Tilletiaceae and from Ustilaginaceae. Tilletiaceae — Tilletia and Urocystis. Ustilaginaceae — Ustilago.

References, etc. Leaf anatomical: Metcalfe 1960; studied by us - L. perenne L., L. rigidum Gaud.

Illustrations. • Lolium rigidum: Bor, Flora of Iraq (1968). • Lolium temulentum, general aspect: Eng. Bot. (1872). • Lolium temulentum var., general aspect: Eng. Bot. 1872). • Lolium temulentum, general aspect. • Lplium multiflorum, as L. bouchéanum: Kunth (1835). • Lolium multiflorum (as L. italicum), general aspect: Eng. Bot. (1872). • Lolium perenne, general aspect: Eng. Bot. (1872). • Leaf auricles (Lolium perenne). • Spikelet close-up (Lolium perenne). Lolium perenne. Spikelet with only one (outer) glume and two open florets; hollowed rachis. • Rachis and spikelet in close-up (Lolium perenne). Lolium perenne. Hollowed rachis (left), the single (‘upper’) glume to the right, the spikelet dorsiventral to the rachis. • Floret and rachilla detail (Lolium perenne). Lolium perenne. Spikelet tip, showing terminal rachilla prolongation within the palea groove of the uppermost floret, flanked by lemma margins. • Lolium perenne, abaxial epidermis of leaf blade: this project. • Lolium perenne, abaxial epidermis of leaf blade: this project. • Lolium perenne, abaxial epidermis of leaf blade, detail: this project. • Lolium perenne, abaxial epidermis of leaf blade, detail: this project. • Grass pollen antigens: Watson and Knox (1976). • Grass pollen antigens: cross-reactions against anti-Lolium serum. IMMUNOELECTROPHORESIS OF GRASS POLLEN EXTRACTS (DIFFUSIBLE ANTIGENS).

Each slide with rabbit antiserum in the trough, Lolium perenne pollen extract (control) in the upper well, and comparable extracts from other genera in the lower wells, as indicated. Results are compared using raw extract (left) with those using boiled extract (right). Antigens allergenic in humans are concentrated in the heat-stable components. For experimental details and discussion of the taxonomic patterns among cross-reactions, see Watson and Knox (1976) and Watson (1983). • Grass pollen antigens: cross-reactions against anti-Lolium serum. IMMUNOELECTROPHRESIS OF GRASS POLLEN EXTRACTS (DIFFUSIBLE ANTIGENS).

Each slide with rabbit antiserum in the trough, Lolium perenne pollen extract (control) in the upper well, and comparable extracts from other genera in the lower wells, as indicated. For experimental details and discussion of the taxonomic patterns among cross-reactios, see Watson and Knox (1976) and Watson (1983). • Heat stable grass pollen antigens (allergens): cross-reactions against anti-Lolium serum. IMMUNOELECTROPHRESIS OF GRASS POLLEN EXTRACTS (DIFFUSIBLE ANTIGENS-HEAT-STABLE COMPONENT).

Each slide with rabbit antiserum in the trough, boiled Lolium perenne pollen extract (control) in the upper well, and comparable boiled extracts from other genera in the lower wells, as indicated. For experimental details and discussion of the taxonomic patterns among cross-reactios, see Watson and Knox (1976) and Watson (1983). • Grass pollen antigens: cross-reactions against anti-Cynodon serum. IMMUNOELECTROPHORESIS OF GRASS POLLEN EXTRACTS (DIFFUSIBLE ANTIGENS).

Each slide with rabbit antiserum in the trough, Cynodon dactylon pollen extract (control) in the upper well, and comparable extracts from other genera in the lower wells, as indicated. Results are compared using raw extract (left) with those using boiled extract (human allergens, right). For experimental details and discussion of the taxonomic patterns among cross-reactions, see Watson and Knox (1976) and Watson (1983). • Grass pollen antigens: cross-reactions against anti-Zea serum. IMMUNOELECTROPHORESIS OF GRASS POLLEN EXTRACTS (DIFFUSIBLE ANTIGENS).

Each slide with rabbit antiserum in the trough, Zea mays pollen extract (control) in the upper well, and comparable extracts from other genera in the lower wells, as indicated. Results are compared using raw extract (left) with those using boiled extract (where availabe, right). Antigens allergenic in humans are concentrated in the heat-stable components. For experimental details and discussion of the taxonomic patterns among cross-reactions, see Watson and Knox (1976) and Watson (1983). • Grass pollen antigens: cross-reactions against anti-Zea serum. • X Festulolium loliaceum (as F. pratensis var. loliacea), = Festuca. pratensis x L. perenne: Eng. Bot. (1872).

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’.

Contents