The grass genera of the world
Habit, vegetative morphology. Perennial; stoloniferous and decumbent. Culms herbaceous; scrambling (over rocks and other vegetation). Leaves non-auriculate. Sheath margins joined. Leaf blades narrow; flat; without cross venation; persistent. Ligule an unfringed membrane; not truncate; 1 mm long.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence few spikeleted; paniculate; open; with capillary branchlets. Inflorescence with axes ending in spikelets. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets unconventional (peculiar, with very long rachilla internodes and tiny glumes); 4.5–7.5 mm long; not noticeably compressed; disarticulating above the glumes; with a distinctly elongated rachilla internode above the glumes and with distinctly elongated rachilla internodes between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairless (scabrid); the rachilla extension naked. Hairy callus absent.
Glumes two; minute; very unequal; shorter than the spikelets; shorter than the adjacent lemmas; hairless; awnless; similar. Lower glume 0 nerved. Upper glume 0 nerved. Spikelets with female-fertile florets only.
Female-fertile florets 2–3. Lemmas lanceolate, broadly acuminate; not becoming indurated (membranous); incised; shortly 2 lobed; not deeply cleft; awned. Awns 1; median; from a sinus; non-geniculate; hairless; much shorter than the body of the lemma. Lemmas hairless; carinate; without a germination flap; 5 nerved. Palea present; relatively long; gaping; apically notched; awnless, without apical setae; not indurated; 2-nerved; 2-keeled. Palea keels wingless. Lodicules present; 2; free; membranous; glabrous; not toothed; not or scarcely vascularized. Stamens 3. Anthers 3.5–3.8 mm long; not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small, or medium sized (3.5–4); compressed laterally. Hilum short. Embryo small. Endosperm hard. Embryo with an epiblast; without a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins meeting.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (costals rectangular); differing markedly in wall thickness costally and intercostally (costals thicker- walled). Mid-intercostal long-cells exaggeratedly fusiform; having straight or only gently undulating walls. Microhairs absent. Stomata absent or very rare. Intercostal short-cells absent or very rare. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies horizontally-elongated smooth (sometimes slightly sinuous).
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade. Midrib with one bundle only. Sclerenchyma all associated with vascular bundles.
Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Poeae. Soreng et al. (2015): Pooideae; Poodae; Poeae. 1 species.
Distribution, phytogeography, ecology. Western tropical South America.
Mesophytic; shade species; glycophytic. In humid montane forest.
References, etc. Leaf anatomical: this project.
Illustrations. • A. procumbens: Nicora & Rúgolo de Agrasar (1987). • A. procumbens, abaxial epidermis of leaf blade: 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: 13th November 2017. delta-intkey.com/grass’.