The grass genera of the world
Habit, vegetative morphology. Perennial; rhizomatous and caespitose. Culms 40–100 cm high; herbaceous; unbranched above. Culm nodes glabrous. Plants unarmed. Leaves non-auriculate. Leaf blades narrow; 1–4 mm wide; flat, or rolled (loosely involute); without abaxial multicellular glands; not pseudopetiolate; without cross venation. Ligule a fringe of hairs. Contra-ligule present (partial, of hairs).
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate; open (5–20 cm long, with few branches); espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets 10–18 mm long; narrowly ovate; compressed laterally to not noticeably compressed; disarticulating above the glumes; disarticulating between the florets; with conventional internode spacings. Rachilla prolonged beyond the uppermost female-fertile floret; hairless (glabrous); the rachilla extension with incomplete florets. Hairy callus present (as the stipe-like base of the lemma).
Glumes two; very unequal; shorter than the spikelets; shorter than the adjacent lemmas; hairless; glabrous; pointed (G1), or not pointed (G2); awnless; carinate (G1), or non-carinate (G2); similar (rather firm, G2 broader). Lower glume 3–5 nerved. Upper glume 7–9 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped. Spikelets without proximal incomplete florets.
Female-fertile florets 6–12. Lemmas similar in texture to the glumes (membranous or thinly papery); not becoming indurated; entire; pointed to blunt; awnless; hairy (below); non-carinate (dorsally rounded); without a germination flap; distinctly 7–9 nerved. Palea present; relatively long; probably apically notched (splitting at maturity); awnless, without apical setae; not indurated (membranous); 2-nerved; 2-keeled. Palea keels narrowly winged (and hollowed between the wings). Lodicules present; 2; free; fleshy; glabrous. Stamens 3; with free filaments (these very long). Anthers short; not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2 (sometimes with a vestigial third style).
Fruit, embryo and seedling. Fruit small (2.5–3 mm long); black; ovate-rounded, ventrally deeply concave; compressed dorsiventrally (concavo-convex); sculptured to smooth (obscurely striate). Hilum short. Pericarp fused. Embryo large; with an epiblast; with a scutellar tail; with an elongated mesocotyl internode. Embryonic leaf margins meeting.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; intercostal. Intercostal papillae over-arching the stomata (at one end); consisting of one oblique swelling per cell (at one end of interstomatals and some intercostal long-cells). Long-cells markedly different in shape costally and intercostally (the costals longer); of similar wall thickness costally and intercostally (medium-thin walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls (and pitted). Microhairs present; elongated; clearly two-celled; chloridoid-type (unusually large). Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhairs (33–)36–39(–42) microns long. Microhair basal cells 24 microns long. Microhairs 10.5–12–14.4 microns wide at the septum. Microhair total length/width at septum 2.7–3.5. Microhair apical cells (7.5–)8.4–9(–12) microns long. Microhair apical cell/total length ratio 0.21–0.27. Stomata common; 21–22.5(–24) microns long. Subsidiaries dome-shaped. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; not paired (solitary); not silicified. Intercostal silica bodies absent. Costal zones with short-cells. Costal short-cells conspicuously in long rows (to solitary - the short-cells mainly very long). Costal silica bodies present in alternate cell files of the costal zones; panicoid-type; mostly dumb-bell shaped (some quite elongated); 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 abaxially only. PCR sheath extensions absent. PCR cell chloroplasts centripetal. Leaf blade with distinct, prominent adaxial ribs to nodular in section (the ribs round-topped); with the ribs more or less constant in size. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups (in all the adaxial furrows); seemingly exclusively in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the bundles); forming figures (all bundles). Sclerenchyma all associated with vascular bundles. The lamina margins with fibres.
Cytology. 2n = 60.
Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Cynodonteae; Gouiniinae. 1 species (V. multinervosa).
Distribution, phytogeography, ecology. Texas.
Species of open habitats. Sandy, open woods.
References, etc. Leaf anatomical: studied by us.
Illustrations. • V. multinervosa: Hitchcock and Chase (1950). • V. multinervosa, abaxial epidermis of leaf blade: this project. • V. multinervosa, TS 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: 11th December 2017. delta-intkey.com/grass’.