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The grass genera of the world

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

Phleum L.

From the Greek phleos, some kind of reed or grass.

Type species: Type: P. pratense L.

Including Achnodon Link, Achnodonton P. Beauv., Chilochloa P. Beauv., Heleochloa P. Beauv., Phalarella Boiss., Plantinia Bub., Stelephuros Adans.

Excluding Maillea, Pseudophleum

Habit, vegetative morphology. Annual, or perennial; rhizomatous, or stoloniferous, or caespitose, or decumbent. Culms 4–150 cm high; herbaceous; sparsely branched above, or unbranched above. The branching simple. Culms tuberous, or not tuberous. Culm nodes glabrous. Culm internodes hollow. Leaves not basally aggregated; non-auriculate. Leaf blades linear; apically cucullate; narrow; 1–10 mm wide; usually flat; not pseudopetiolate; without cross venation; persistent; rolled in bud. Ligule present; an unfringed membrane; truncate, or not truncate; 1.5–6 mm long.

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

Inflorescence. Inflorescence paniculate; contracted; capitate, or more or less ovoid, or spicate; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund.

Female-fertile spikelets. Spikelets 1.6–5 mm long; strongly compressed laterally; disarticulating above the glumes. Rachilla prolonged beyond the uppermost female-fertile floret, or terminated by a female-fertile floret; the rachilla extension when present, naked. Hairy callus absent. Callus short.

Glumes two; more or less equal; long relative to the adjacent lemmas (exceeding them); pointed; shortly awned; carinate; similar (membranous, the margins overlapping for most of their length). Lower glume 3 nerved. Upper glume 3 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.

Female-fertile florets 1. Lemmas less firm than the glumes (membranous); not becoming indurated; entire; blunt (truncate or obtuse); awnless; hairy, or hairless (glabrous to densely ciliate); non-carinate; 5–7 nerved. Palea present; relatively long; entire to apically notched; awnless, without apical setae; not indurated; 1-nerved, or 2-nerved; keel-less. Lodicules present; 2; free; membranous; glabrous; toothed; not or scarcely vascularized. Stamens 3. Anthers 0.3–2.3 mm long; not penicillate. Ovary apically glabrous. Styles fused, or free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit small. Hilum short. Embryo small; not waisted. Endosperm liquid in the mature fruit; containing compound starch grains. Embryo with an epiblast; without a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins meeting.

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

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 markedly sinuous walls. Microhairs absent. Stomata common; (36–)42–45 microns long. Subsidiaries parallel-sided. Guard-cells overlapped by the interstomatals. Intercostal short-cells absent or very rare (rare); not paired (usually solitary); not silicified. Crown cells absent (but some reduced prickles approach these). Costal short-cells conspicuously in long rows. Costal silica bodies horizontally-elongated crenate/sinuous, or horizontally-elongated smooth, or rounded; not sharp-pointed.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade. 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. Many of the smallest vascular bundles unaccompanied by sclerenchyma, or all the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; nowhere forming ‘figures’. Sclerenchyma all associated with vascular bundles.

Phytochemistry. Tissues of the culm bases with little or no starch. Fructosans predominantly long-chain. Leaves without flavonoid sulphates (2 species).

Cytology. Chromosome base number, x = 7. 2n = 10 (rarely), or 14, or 28, or 42. 2, 4, and 6 ploid. Chromosomes ‘large’. Haploid nuclear DNA content 1.6–1.7 pg (2 species). Mean diploid 2c DNA value 3.4 pg (1 species).

Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Aveneae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Poinae. 15 species.

Distribution, phytogeography, ecology. Temperate Eurasia, America.

Commonly adventive. Mostly mesophytic; species of open habitats; mostly glycophytic, or halophytic. Meadows and dry places, P. arenarium in coastal sand.

Economic aspects. Cultivated fodder: P. bertolonii, P. pratense (Timothy). Lawns and/or playing fields: P. bertolonii.

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

References, etc. Leaf anatomical: Metcalfe 1960 and this project.

Illustrations. • P. pratense: Gardner, 1952. • P. phleoides (as P. boehmeri): general aspect, Eng. Bot. (1872). • P. pratense, general aspect: Eng. Bot. (1872). • P. alpinum, general aspect: Eng. Bot. (1872). • P. arenarium, general aspect: Eng. Bot. (1872). • Pollen antigens: Watson and Knox (1976)


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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’.

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