The grass genera of the world
Habit, vegetative morphology. Slender annual; caespitose. Culms 10–40 cm high; herbaceous; branched above. Culm nodes glabrous. Leaves not basally aggregated; non-auriculate. Leaf blades linear; narrow; 2–3 mm wide; flat, or rolled; without abaxial multicellular glands; without cross venation. Ligule present; a fringe of hairs. Contra-ligule absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant (theoretically), or all alike in sexuality; hermaphrodite, or hermaphrodite and sterile (by recognition of well disguised vestigial spikelets); overtly heteromorphic, or homomorphic (each manifest spikelet being subtended at its base by a tiny hyaline bract, (?)representing a reduced spikelet or branch system); all in heterogamous combinations.
Inflorescence. Inflorescence a single raceme (a bottlebrush); espatheate (but bracteate); not comprising partial inflorescences and foliar organs. Spikelet-bearing axes spikelike; persistent. Spikelets associated with bractiform involucres (or at least, each with one small bract). The involucres persistent on the rachis. Spikelets ostensibly solitary; shortly pedicellate (erect, the pedicel becoming the callus).
Female-fertile spikelets. Spikelets 4–7 mm long; compressed laterally; falling with the glumes (and with the pungent pedicel). Rachilla prolonged beyond the uppermost female-fertile floret; hairless; the rachilla extension with incomplete florets. Hairy callus present (1–1.2 mm long). Callus of the spikelet short; pointed.
Glumes two; more or less equal; shorter than the adjacent lemmas; hairy; awned (with long, straight, scabrid terminal awns); somewhat carinate; similar (hairy, asymmetric, truncate or bilobed). Lower glume 2 nerved. Upper glume 3 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets 1–3; awned (reduced to a cluster of awns). Spikelets without proximal incomplete florets.
Female-fertile florets 1. Lemmas similar in texture to the glumes (membranous); not becoming indurated; entire, or incised; not deeply cleft; awned. Awns 1; median; from a sinus (this slight), or apical; non-geniculate; hairless (scabrid); much longer than the body of the lemma. Lemmas hairless; glabrous; non-carinate (dorsally rounded); without a germination flap; 3 nerved, or 5 nerved. Palea present; relatively long; entire (pointed); with apical setae (glabrous); not indurated (membranous); 2-nerved; 2-keeled. Lodicules present; free; fleshy; ciliate, or glabrous. Stamens with free filaments (these long). Anthers short; not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit banana-shaped. Embryo 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 absent. Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally (thick walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls (and pitted). Microhairs present; elongated; clearly two-celled; panicoid-type; 36–39–45 microns long. Microhair basal cells 18 microns long. Microhairs (5.1–)5.4–5.7(–6) microns wide at the septum. Microhair total length/width at septum 6.3–7.6. Microhair apical cells 19.5–21 microns long. Microhair apical cell/total length ratio 0.43–0.54. Stomata common; 19–22.5 microns long. Subsidiaries mostly 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 predominantly paired. Costal silica bodies present throughout the costal zones; rounded to crescentic (predominantly more or less imperfect saddles, intergrading with the other forms); not sharp-pointed.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+. PCR sheath outlines uneven. PCR sheaths of the primary vascular bundles interrupted; interrupted abaxially only. PCR sheath extensions present. Maximum number of extension cells 1–2. Mesophyll with fusoids (in the sense that a PCR cell on either side of each bundle protrudes laterally, constituting a wing which approaches that of the adjacent bundle). The fusoids an integral part of the PBS. Leaf blade adaxially flat. Midrib conspicuous to not readily distinguishable (a slightly larger bundle and keel); with one bundle only. Bulliforms present in discrete, regular adaxial groups (between each bundle pair); in simple fans (the median cells deeply penetrating). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the bundles); forming figures (all the bundles). Sclerenchyma all associated with vascular bundles. The lamina margins with fibres.
Special diagnostic feature. The inflorescence a spicate raceme, with each spikelet subtended at its base by a tiny hyaline bract: Madagascar.
Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae. 1 species (V. madagascariensis).
Distribution, phytogeography, ecology. Madagascar.
Xerophytic; species of open habitats.
References, etc. Leaf anatomical: studied by us.
Special comments. Fruit data wanting. Illustrations. • Abaxial epidermis of leaf blade of V. madagascariensis: this project. • TS leaf blade of V. madagascariensis: 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’.