The grass genera of the world
Habit, vegetative morphology. Perennial; caespitose. Culms 40 cm high; herbaceous; unbranched above. Plants unarmed. Leaves not basally aggregated; non-auriculate. Leaf blades linear (acuminate, rigid, subulate-tipped); narrow; 2–7 mm wide; rolled (convolute), or acicular (towards the tip); without abaxial multicellular glands; not pseudopetiolate; without cross venation; persistent. Ligule a fringe of hairs (dense). Contra-ligule absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate; contracted; spicate (5–10 cm long in material seen); espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; very shortly pedicellate.
Female-fertile spikelets. Spikelets 2.5 mm long; compressed laterally; disarticulating above the glumes; with conventional internode spacings. Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes two; more or less equal; shorter than the adjacent lemmas (or at least, somewhat shorter); hairy (slightly, on the upper third of the mid-nerve); pointed; awnless (not mucronate); carinate; similar (lanceolate, hyaline). Lower glume 1 nerved. Upper glume 1 nerved. Spikelets with female-fertile florets only.
Female-fertile florets 1. Lemmas acuminate; similar in texture to the glumes (hyaline); not becoming indurated; entire; pointed; mucronate (to aristulate); hairy, or hairless; carinate; without a germination flap; 1 nerved. Palea present; relatively long; apically notched; awnless, without apical setae (glabrous); not indurated (hyaline, delicate); 2-nerved (but the veins very scanty); 2-keeled. Lodicules absent. Stamens 3. Anthers relatively long; not penicillate; without an apically prolonged connective. Ovary apically hairy; with a conspicuous apical appendage (beaked). Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit small; ellipsoid. Pericarp free (becoming swollen when wet, extruding the seed).
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous (the intercostal zones in deep grooves, their detailed histology inaccessible). Papillae present; intercostal. Intercostal papillae consisting of one symmetrical projection per cell (thick-walled). Long-cells differing markedly in wall thickness costally and intercostally (costals thicker-walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls (and pitted, with abundant pits in outer walls). Microhairs present (in deep, narrow abaxial grooves, obscured by thick walled macrohairs and blunt prickles); more or less spherical to elongated; clearly two-celled; chloridoid-type. Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhairs 30–36 microns long. Microhair basal cells 2 microns long. Microhairs 13.5–19.5 microns wide at the septum. Microhair total length/width at septum 1.8–2.2. Microhair apical cells 15–18 microns long. Microhair apical cell/total length ratio 0.5–0.55. Stomata common; 15–18 microns long. Subsidiaries high dome-shaped and triangular. Guard-cells overlapping to flush with the interstomatals. Costal zones with short-cells. Costal short-cells predominantly paired. Costal silica bodies present throughout the costal zones; rounded, saddle shaped, tall-and-narrow, and crescentic; not sharp-pointed.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+. PCR sheaths of the primary vascular bundles interrupted; interrupted both abaxially and adaxially. PCR sheath extensions absent. Mesophyll traversed by columns of colourless mesophyll cells. Leaf blade nodular in section (deep, narrow abaxial grooves opposite the broader adaxial furrows); with the ribs very irregular in sizes (large flat-topped ribs alternating with small pointed ones). Midrib not readily distinguishable; with one bundle only; with colourless mesophyll adaxially (exhibiting extensive blocks of colourless tissue adaxially and abaxially with all the bundles, each block bounded adaxially and abaxially by sclerenchyma and laterally by the rows of PCR cells). Bulliforms present in discrete, regular adaxial groups; associated with colourless mesophyll cells to form deeply-penetrating fans (these connected with the traversing columns of colourless cells). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with the primaries, the smaller bundles with only abaxial girders); forming figures (heavily I-shaped in the main bundles). Sclerenchyma all associated with vascular bundles. The lamina margins with fibres.
Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Zoysieae; Zoysiinae. 1 species (U. setulosa).
Distribution, phytogeography, ecology. Northeast tropical Africa.
Species of open habitats; halophytic. In coastal sand.
References, etc. Leaf anatomical: studied by us.
Special comments. Fruit data wanting. Illustrations. • U. setulosa: S. Hameed, Fl. of Pakistan www.efloras.org)
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’.