The grass genera of the world
Habit, vegetative morphology. Perennial; rhizomatous and caespitose. Culms 30–50 cm high; herbaceous; unbranched above. Culm internodes solid. Rhizomes pachymorph. Leaves mostly basal; auriculate (on the sheaths); without auricular setae. Leaf blades narrowly lanceolate (to oblong-lanceolate); broad; (40–)60–100 mm wide (18–40 cm long); cordate; flat; pseudopetiolate (the petioles up to 25 cm); palmately veined; cross veined; seemingly persistent (but more or less articulated); rolled in bud. Ligule a fringe of hairs. Contra-ligule absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence spicate, cymoid, with 2–5 spikelets in the axil of each bract; spatheate (and spatheolate); a complex of partial inflorescences and intervening foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; secund (in the partial inflorescences); pedicellate.
Female-fertile spikelets. Spikelets unconventional (apparently lacking glumes, exhibiting an upper and a lower bract and a perigonate annulus, all presenting interpretive problems). Rachilla terminated by a female-fertile floret.
Glumes absent. Spikelets with female-fertile florets only.
Female-fertile florets 1. Lemmas (if the lower bract is seen as such) leathery, ovate, tessellate-nerved; not becoming indurated; non-carinate; without a germination flap; many nerved. Palea (if the upper bract be so interpreted) present; forming a closed tube below, enclosing the flower; several nerved; keel-less. Lodicules present; joined (confluent, in the form of an annulus - if the annulus be so interpreted); ciliate (in that the annulus is fringed). Stamens 4. Anthers 3–5 mm long. Ovary apically glabrous. Stigmas 1.
Fruit, embryo and seedling. Fruit medium sized (up to 10 mm long); oblong to rectangular; shallowly longitudinally grooved; compressed laterally. Hilum long-linear. Embryo large (nearly as long as the fruit). Endosperm containing compound starch grains. Embryo with an epiblast; with a scutellar tail (inconspicuous); with a negligible mesocotyl internode. Embryonic leaf margins meeting.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Intercostal zones exhibiting many atypical long-cells (rather short). Mid-intercostal long-cells having markedly sinuous walls. Microhairs present; more or less spherical to elongated; clearly two-celled; panicoid-type; (74–)80–90(–115) microns long. Microhair apical cells (45–)48–60(–63) microns long. Microhair apical cell/total length ratio about 0.64. Stomata common. Subsidiaries low dome-shaped and triangular. Intercostal short-cells common; in cork/silica-cell pairs; silicified. Intercostal silica bodies tall-and-narrow. Costal short-cells neither distinctly grouped into long rows nor predominantly paired (in series of 2–4). Costal silica bodies horizontally-elongated smooth and rounded.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; with arm cells; with fusoids. The fusoids external to the PBS. Leaf blade blade with slight ribs and furrows adaxially. Midrib conspicuous (projecting adaxial rib); having complex vascularization (a large abaxial bundle, and 2 smaller ones in a line above it). Bulliforms present in discrete, regular adaxial groups to not present in discrete, regular adaxial groups; in groups of the irregular type. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming figures (incomplete anchors). Sclerenchyma all associated with vascular bundles.
Special diagnostic feature. Inflorescence of 23 glumeless, bracteate spikelets, the lodicules represented by a fringed annulus.
Cytology. Chromosome base number, x = 9. 2n = 36.
Classification. Watson & Dallwitz (1994): Bambusoideae; Oryzodae; Anomochloeae. Soreng et al. (2015): Anomochlooideae; Anomochloeae. 1 species.
Distribution, phytogeography, ecology. Tropical America.
Shade species. In forests.
References, etc. Morphological/taxonomic: Judziewcz and Soderstrom 1989. Leaf anatomical: Metcalfe 1960, Judziewcz and Soderstrom 1989.
Illustrations. • A. marantoidea (Fl. Bras. 2(2), 1871)
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’.