The grass genera of the world
Including Nevroctola Raf., Trisiola Raf. (1817), Triunila Raf.
Habit, vegetative morphology. Perennial; rhizomatous, or stoloniferous. Culms 100–220 cm high; herbaceous. Culm internodes solid to hollow. Sheath margins free. Leaf blades harsh; narrow; without abaxial multicellular glands. Ligule a fringe of hairs.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets; exposed-cleistogamous, or chasmogamous.
Inflorescence. Inflorescence of spicate main branches, or paniculate; contracted (the crowded branches overlapping), or open; espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; long to short pedicellate.
Female-fertile spikelets. Spikelets 10–25 mm long; compressed laterally; falling with the glumes; not disarticulating between the florets; with conventional internode spacings. Rachilla prolonged beyond the uppermost female-fertile floret.
Glumes two; shorter than the spikelets; pointed; awnless; carinate; similar (narrow, rigid). Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets, or both distal and proximal to the female-fertile florets. The distal incomplete florets (when present) merely underdeveloped. Spikelets with proximal incomplete florets. The proximal incomplete florets 3–5. The proximal lemmas similar in texture to the female-fertile lemmas.
Female-fertile florets 7–15. Lemmas acute or acuminate; papery or leathery; not becoming indurated; entire; pointed; awnless; carinate (and compressed); 7–10 nerved. Palea present; relatively long; awnless, without apical setae; 2-nerved; 2-keeled. Palea keels winged; hairy (ciliate). Lodicules present; 2; free; fleshy; glabrous; heavily vascularized, or not or scarcely vascularized. Stamens 3.
Fruit, embryo and seedling. Fruit ellipsoid. Pericarp free. Embryo large; waisted; without an epiblast; with a scutellar tail; with an elongated mesocotyl internode; with more than one scutellum bundle. Embryonic leaf margins meeting.
First seedling leaf with a well-developed lamina. The lamina narrow; erect.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally to markedly different in shape costally and intercostally (the costals narrower, more regularly rectangular); of similar wall thickness costally and intercostally (fairly thick walled). Mid-intercostal long-cells rectangular, or rectangular and fusiform (in U. paniculata); having markedly sinuous walls. Microhairs absent (but present adaxially); chloridoid type. Stomata common; 21–33 microns long. Subsidiaries low to high dome-shaped. Guard-cells overlapped by the interstomatals (and somewhat sunken, in U. paniculata), or overlapping to flush with the interstomatals (in U. pittieri). Intercostal short-cells common; in cork/silica-cell pairs and not paired; silicified (but no perfect silica bodies seen), or not silicified. Intercostal silica bodies present and perfectly developed. Macrohairs and prickles absent. Crown cells absent. Costal zones with short-cells. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies poorly developed (and scarce, in the material of both species examined); present throughout the costal zones; where detectable rounded to saddle shaped (well developed saddles adaxially); sometimes sharp-pointed, or not sharp-pointed.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+. PCR sheath outlines even. PCR sheaths of the primary vascular bundles interrupted; interrupted both abaxially and adaxially. PCR sheath extensions absent. PCR cell chloroplasts with well developed grana; probably centrifugal/peripheral (? - judging from inadequate material). Mesophyll with radiate chlorenchyma; traversed by columns of colourless mesophyll cells (the columns wide). Leaf blade with distinct, prominent adaxial ribs; with the ribs more or less constant in size (round to flat topped, in U. pittieri), or with the ribs very irregular in sizes (tall and flat topped, with hollowed sides in U. paniculata). Midrib not readily distinguishable; with one bundle only. The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups; associated with colourless mesophyll cells to form deeply-penetrating fans (these in every furrow, linked with the colourless columns). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (U. pittieri), or absent (U. paniculata, where the upper region of each of the tall ribs is occupied by lightly lignified colourless tissue, containing a few scattered thick-walled fibres, linking the bundle with an adaxial strand); in U. pitteri forming figures (every bundle being associated with a substantial I). Sclerenchyma not all bundle-associated. The extra sclerenchyma in abaxial groups; abaxial-hypodermal, the groups continuous with colourless columns. The lamina margins with fibres.
Cytology. Chromosome base number, x = 10. 2n = 40.
Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Eragrostideae; Unioliinae. 2 species.
Distribution, phytogeography, ecology. North America, West Indies.
Species of open habitats; halophytic. Sand dunes and salt flats.
Economic aspects. U. paniculata a significant sandbinder.
References, etc. Morphological/taxonomic: Yates 1966a. Leaf anatomical: studied by us - U. paniculata L., U. pittieri Hack.
Special comments. Fruit data wanting. Illustrations. • U. paniculata (as maritima), with Schismus marginatus (= barbatus), Megastachya owariensis (= mucronata) and Eleusine coracana: P. Beauv. (1812). • U. latifolia: Hitchcock and Chase (1950)
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’.