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The grass genera of the world

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

Tsvelevia E. Alekseev

~ Poa kerguelensis, Poa, Festuca

Habit, vegetative morphology. Perennial; densely caespitose. Culms 4–10 cm high; herbaceous; unbranched above. Young shoots intravaginal. Leaves non-auriculate. Sheath margins free. Sheaths scarious. Leaf blades linear; narrow; 0.5–0.7 mm wide; folded to rolled (folded to involute); not pseudopetiolate; without cross venation; persistent; once-folded in bud. Ligule an unfringed membrane; not truncate; 0.7–1.5 mm long. Contra-ligule absent.

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

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

Female-fertile spikelets. Spikelets 3.5–4 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.

Glumes two; very unequal (to almost equal); shorter than the spikelets to about equalling the spikelets; shorter than the adjacent lemmas; hairless; glabrous; pointed; not subulate; awnless; carinate; similar. Lower glume about 0.6–0.75 times the length of the upper glume; shorter than the lowest lemma to about equalling the lowest lemma; 1 nerved. Upper glume 3 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped; awnless. Spikelets without proximal incomplete florets.

Female-fertile florets 2–3. Lemmas similar in texture to the glumes (thin); not becoming indurated; entire to incised; pointed; if incised, 2–3 lobed; not deeply cleft; awnless; hairy (especially on the nerves); carinate; without a germination flap; 3 nerved; with the nerves non-confluent. Palea present; relatively long; tightly clasped by the lemma; apically notched; awnless, without apical setae; textured like the lemma; not indurated; 2-nerved; 2-keeled. Palea keels wingless; hairy (below). Lodicules present; 2; free; membranous; glabrous; toothed. Stamens 3. Anthers 0.5–0.7 mm long; not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2; white.

Fruit, embryo and seedling. Fruit free from both lemma and palea; small (about 2 mm long); longitudinally grooved; slightly compressed dorsiventrally. Hilum long-linear. Embryo small.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells of similar wall thickness costally and intercostally (thick walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls (heavily pitted). Microhairs absent. Stomata absent or very rare. Intercostal short-cells common; in cork/silica-cell pairs. Costal zones with short-cells. Costal short-cells predominantly paired (with only a few short rows). Costal silica bodies rounded and crescentic; not sharp-pointed.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade. Leaf blade adaxially flat. Midrib conspicuous (by the rounded abaxial keel, and flanking ‘hinges’); with one bundle only. Bulliforms not present in discrete, regular adaxial groups (other than the midrib ‘hinges’). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders absent (each bundle with a small abaxial strand only). Sclerenchyma all associated with vascular bundles.

Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Poeae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Poinae. 1 species (T. kerguelensis).

Distribution, phytogeography, ecology. Chatham Islands.

Xerophytic; halophytic. Maritime sand.

References, etc. Morphological/taxonomic: Alekseev 1985. Leaf anatomical: studied by us.

Illustrations. • Abaxial epidermis of leaf blade of T. kerguelensis: this project

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: 11th December 2017.’.