The grass genera of the world
Habit, vegetative morphology. Perennial; caespitose. Culms herbaceous. Leaves non-auriculate (?). Leaf blades narrow; setaceous; without cross venation. Ligule an unfringed membrane.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality.
Inflorescence. Inflorescence paniculate; oblong, contracted; espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets compressed laterally; disarticulating above the glumes; not disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Hairy callus absent.
Glumes two; very unequal; shorter than the adjacent lemmas; pointed; awnless; carinate. Lower glume 1 nerved. Upper glume 3 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets 4–7; clearly specialised and modified in form; awned (the prominent awns of the sterile lemmas apparently functioning to aid disperal).
Female-fertile florets 2–3(–4). Lemmas firmly membranous; incised; 2 lobed; awned. Awns 1; median; dorsal; from near the top, or from well down the back; non-geniculate. Lemmas hairless; carinate to non-carinate; without a germination flap; 5 nerved. Palea present; gaping; 2-nerved. Lodicules present; 2; free; membranous; glabrous; toothed; not or scarcely vascularized. Stamens 2–3. Ovary apically glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit small, or medium sized (4 mm long); compressed dorsiventrally. Hilum long-linear. Embryo small. Endosperm hard; containing compound starch grains.
Abaxial leaf blade epidermis. Papillae absent. Long-cells markedly different in shape costally and intercostally (the costals much smaller and narrower); of similar wall thickness costally and intercostally (walls thick, pitted). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs absent. Stomata absent or very rare (present in the furrows adaxially - with parallel-sided subsidiaries). Intercostal short-cells absent or very rare. Thick walled prickles common costally. Crown cells absent. Costal silica bodies poorly developed; perhaps tall-and-narrow, or crescentic, or poorly developed in material seen.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll without adaxial palisade. Leaf blade with distinct, prominent adaxial ribs; with the ribs very irregular in sizes. Midrib not readily distinguishable; with one bundle only. The lamina symmetrical on either side of the midrib. Bulliforms unclear in the poor material seen. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders absent (some bundles with an abaxial strand only, others with a small adaxial strand as well). Sclerenchyma all associated with vascular bundles (except at the blade margins).
Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Aveneae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Loliinae. 1 species (D. floribunda).
Distribution, phytogeography, ecology. Peru.
Species of open habitats. In high altitude grassland.
References, etc. Leaf anatomical: studied by us.
Illustrations. • D. floribunda: Nicora & Rúgolo de Agrasar (1987)
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. delta-intkey.com/grass’.