The grass genera of the world
Habit, vegetative morphology. Perennial; caespitose. The flowering culms leafy (but with only 1–3 developed blades). Culms 20–50 cm high; unbranched above. Culm nodes hairy. Culm internodes solid (the middle internodes much elongated). Rhizomes pachymorph. Plants unarmed. Young shoots extravaginal and intravaginal. Leaves mostly basal; with auricular setae. Leaf blades ovate-lanceolate, or elliptic (acuminate); broad; 30–50 mm wide (and 10–21 cm long); not cordate, not sagittate (asymmetrically rounded at base); pseudopetiolate (pulvinate, twisted through 180 degrees); cross veined; rolled in bud. Ligule present (thick); 0.5–1.2 mm long. Contra-ligule absent.
Reproductive organization. Plants monoecious with all the fertile spikelets unisexual; without hermaphrodite florets. The spikelets of sexually distinct forms on the same plant (male and female); female-only and male-only. The male and female-fertile spikelets mixed in the inflorescence (each infloresence unit with 2-several female spikelets and 1–2 males). The spikelets overtly heteromorphic; all in heterogamous combinations.
Inflorescence. Inflorescence indeterminate (a synflorescence); paniculate (terminal, of reduced racemelike panicles); contracted; rigid-fusiform; spatheate (spatheoles, etc. hidden within within the uppermost sheaths); a complex of partial inflorescences and intervening foliar organs (but not obviously so, without dissection). Spikelet-bearing axes reduced, mixed-sex racemes; persistent. Spikelets paired; not secund; subsessile, or pedicellate; consistently in long-and-short combinations; unequally pedicellate in each combination. The shorter spikelets female-only. The longer spikelets male-only.
Female-sterile spikelets. Male spikelets smaller than the females, without glumes, lemmas 7 nerved, florets with 3 fertile stamens and non-penicillate anthers and 3 staminodes. Rachilla of male spikelets terminated by a male floret. The male spikelets without glumes; without proximal incomplete florets; 1 floreted. Male florets 1; 3 staminate, or 6 staminate (if the 3 staminodes are called stamens).
Female-fertile spikelets. Spikelets 9.5–11.5 mm long; compressed laterally to not noticeably compressed (? depressed); disarticulating above the glumes; with conventional internode spacings. Rachilla terminated by a female-fertile floret (and no elongated internode above the glumes). Hairy callus absent. Callus absent.
Glumes two; more or less equal; long relative to the adjacent lemmas (about equalling them); free; hairless (glabrous, short-hispid at tip); pointed; awnless; non-carinate; similar (lanceolate-acute, leathery). Lower glume 5–6 nerved. Upper glume 5–7 nerved. Spikelets with female-fertile florets only.
Female-fertile florets 1. Lemmas narrowly lanceolate-acuminate; decidedly firmer than the glumes; becoming indurated (leathery, becoming crustaceous); entire; pointed; awnless; hairy (covered with long appressed hairs); non-carinate; having the margins inrolled against the palea (and enclosing it); (5–)7(–8) nerved. Palea present (but enclosed, elliptic-acuminate); relatively long; convolute around the flower; entire; awnless, without apical setae; indurated; several nerved (2–4); keel-less (convolute, villous). Lodicules present; 3, or 4; free; glabrous; not toothed; heavily vascularized. Stamens 0 (3 minute staminodes, alternating with the lodicules). Ovary apically glabrous (but the style hairy below middle). Styles fused (the ovary attenuate into one long slender style). Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea (but enclosed); medium sized (5.5 mm long); compressed dorsiventrally (ventrally). Hilum long-linear. Embryo small. Endosperm containing compound starch grains.
Seedling with a short mesocotyl. First seedling leaf without a lamina (the seedling with two sheaths).
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present. Intercostal papillae over-arching the stomata; several per cell (more than 1 row per cell). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; clearly two-celled, or uniseriate (i.e. some 3-celled); panicoid-type. Stomata common (in bands alongside veins). Subsidiaries papillate; triangular. Intercostal short-cells common; in cork/silica-cell pairs; silicified. Intercostal silica bodies tall-and-narrow and oryzoid-type. Costal short-cells conspicuously in long rows (a few pairs and short rows). Costal silica bodies saddle shaped, or oryzoid (some tending to this form), or panicoid-type (some); when panicoid type, tending to cross shaped; not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with arm cells; with fusoids (large). Leaf blade with distinct, prominent adaxial ribs (wide, rounded); with the ribs more or less constant in size. Midrib conspicuous (larger rib); having a conventional arc of bundles (1 or 2 small bundles each side of median). Bulliforms present in discrete, regular adaxial groups. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the bundles); forming figures.
Cytology. Chromosome base number, x = 11. 2n = 22. 2 ploid.
Classification. Watson & Dallwitz (1994): Bambusoideae; Oryzodae; Olyreae. Soreng et al. (2015): Bambusoideae; Bambusodae; Olyreae; Olyrinae. 1 species (M. tecta).
Distribution, phytogeography, ecology. Panama.
References, etc. Morphological/taxonomic: Calderón and Soderstrom 1973.
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’.