The grass genera of the world
Including Trisetum pumilum (Desf.) Kunth, Koeleria pumila (Desf.) Domin
Habit, vegetative morphology. Annual; caespitose. Culms 5–35 cm high; herbaceous; unbranched above. Culm nodes glabrous. Leaves not basally aggregated; non-auriculate. Sheaths somewhat inflated. Leaf blades linear; narrow; 2.5–3 mm wide; flat; without cross venation; persistent. Ligule an unfringed membrane (but ciliolate); not truncate; about 1.5 mm long. Contra-ligule absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality.
Inflorescence. Inflorescence paniculate; contracted; more or less irregular. Primary inflorescence branches borne distichously. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelets not secund; pedicellate; imbricate.
Female-fertile spikelets. Spikelets 2.7–3.6 mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets; with conventional internode spacings. Rachilla prolonged beyond the uppermost female-fertile floret; hairy; the rachilla extension with incomplete florets. Hairy callus present. Callus short.
Glumes two; more or less equal; about equalling the spikelets; long relative to the adjacent lemmas; hairy (G1 densely pubescent over the back, G2 long-ciliate only on the keel); without conspicuous tufts or rows of hairs; pointed; awnless (but mucronate); carinate; very dissimilar (the lower densely pubescent, the upper glabrous save on the keel). Lower glume about equalling the lowest lemma; 1 nerved, or 3 nerved. Upper glume 3 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets 1 (the rachilla prolongation terminating in a reduced floret, or part of one); merely underdeveloped (though sometimes awned); awned, or awnless.
Female-fertile florets 2. Lemmas complanate; less firm than the glumes to similar in texture to the glumes (thinly membranous to hyaline - cf. the upper glume); not becoming indurated; incised; pointed; shortly 2 lobed; not deeply cleft; awned. Awns 1; median; dorsal; from near the top; non-geniculate; hairless; much shorter than the body of the lemma; entered by one vein. Awn bases not twisted. Lemmas hairless; glabrous to scabrous; carinate; without a germination flap; 5 nerved; with the nerves non-confluent. Palea present; conspicuous but relatively short; gaping; apically notched; awnless, without apical setae; somewhat thinner than the lemma (hyaline); not indurated; 2-nerved; 2-keeled. Palea keels wingless. Lodicules present; 2; free; membranous; glabrous; not or scarcely vascularized. Stamens 3. Anthers about 0.4–0.6 mm long (ovoid); not penicillate; without an apically prolonged connective. Ovary apically glabrous. Stigmas 2; white.
Fruit, embryo and seedling. Fruit small. Hilum short (?). Embryo small.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (the costals narrower); of similar wall thickness costally and intercostally. Mid-intercostal long-cells fusiform; having straight or only gently undulating walls. Microhairs absent. Stomata common (but mostly alongside the costae). Subsidiaries parallel-sided. Guard-cells overlapped by the interstomatals. Intercostal short-cells absent or very rare. Costal zones with short-cells. Costal short-cells conspicuously in long rows (in places), or neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies horizontally-elongated crenate/sinuous to horizontally-elongated smooth; not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma. Leaf blade with distinct, prominent adaxial ribs; with the ribs more or less constant in size. Midrib not readily distinguishable; with one bundle only. The lamina symmetrical on either side of the midrib. Bulliforms not present in discrete, regular adaxial groups (seemingly, in the poor material seen). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with the main bundles only - the minor bundles with strands); forming figures. Sclerenchyma all associated with vascular bundles.
Special diagnostic feature. Panicle loose, or if dense then interrupted, neither cylindrical nor ovoid: awns usually present, usually twisted, usually distinctly dorsal, conspicuous if inflorescence compact.
Cytology. Chromosome base number, x = 7. 2n = 14. 2 ploid. Chromosomes large.
Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Aveneae. Soreng et al. (2015): cf. Pooideae (? - as a synonym); Poodae; Poeae; Aveninae.
Distribution, phytogeography, ecology. Central and southern Spain.
Commonly adventive. Glycophytic.
References, etc. Leaf anatomical: this project.
Illustrations. • General aspect: Gibbs Russell et al., 1990. • Inflorescence. • Spikelets
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: 13th November 2017. delta-intkey.com/grass’.