The grass genera of the world
Habit, vegetative morphology. Perennial; caespitose. Culms 13–57 cm high; herbaceous; unbranched above (though branching below). Culm nodes glabrous. Culm leaves present. Culm internodes solid. Plants unarmed. Young shoots intravaginal. Leaves mostly basal; non-auriculate. Leaf blades greatly reduced (on upper culms), or not all greatly reduced; linear-lanceolate; narrow; 2–4 mm wide (to 6 cm long); rolled (involute); without abaxial multicellular glands; not pseudopetiolate; without cross venation; persistent. Ligule an unfringed membrane (in L. parva), or a fringed membrane (in L. digitata); when unfringed truncate; 0.1–0.4 mm long. Contra-ligule absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant (sometimes? - see below), or all alike in sexuality.
Inflorescence. Inflorescence of spicate main branches (consisting of slender spike-like racemes); digitate. Primary inflorescence branches 2–8. Inflorescence espatheate, or spatheate (in that the spikelets are sometimes subtended by very minute, sparsely hairy, hyaline scales - vestigial bracts or spikelets?); not comprising partial inflorescences and foliar organs. The racemes spikelet bearing to the base. Spikelet-bearing axes with very slender rachides; persistent. Spikelets solitary; secund; biseriate; shortly pedicellate, or subsessile; somewhat not imbricate.
Female-fertile spikelets. Spikelets 3.5–6 mm long; adaxial; compressed laterally; disarticulating above the glumes; disarticulating between the florets; with distinctly elongated rachilla internodes between the florets (between L1 and L2 and above L2). Rachilla prolonged beyond the uppermost female-fertile floret; hairy, or hairless; the rachilla extension with incomplete florets. Hairy callus present (minutely bearded). Callus short; pointed.
Glumes two; very unequal (G1 shorter), or more or less equal; shorter than the spikelets to about equalling the spikelets; shorter than the adjacent lemmas (G1, sometimes), or long relative to the adjacent lemmas; hairless; glabrous (the keel scabrous); pointed (acute or acuminate); awnless; carinate; similar (linear-lanceolate, membranous). Lower glume shorter than the lowest lemma to about equalling the lowest lemma; 1 nerved. Upper glume 1 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets about 4; clearly specialised and modified in form (forming a tuft which remains attached to the upper fertile floret); awned (reduced to awns).
Female-fertile florets 1, or 2 (the second floret sometimes male-only). Lemmas less firm than the glumes (thinly membranous); not becoming indurated; incised; 2 lobed (two-toothed); not deeply cleft; awned. Awns 1; median; from a sinus; non-geniculate; straight, or recurving (fine); hairless (scabrous); about as long as the body of the lemma to much longer than the body of the lemma; entered by one vein. Lemmas hairy; carinate; without a germination flap; 3 nerved. Palea present; relatively long (reaching the bases of the lemma lobes); entire; awnless, without apical setae; not indurated (thinly membranous or hyaline); 2-nerved; 2-keeled. Palea keels wingless; scabrous (or sparsely ciliate). Lodicules present; free; somewhat fleshy; glabrous; conspicuously toothed; not or scarcely vascularized. Stamens 3. Anthers 1.5 mm long (i.e. relatively large); not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2; brown.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small (1.8 mm long); fusiform; not noticeably compressed. Hilum short. Pericarp loosely adherent (easily removable after soaking). Embryo large (a little more than 1/3 the length of the fruit); not waisted.
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. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; panicoid-type to chloridoid-type (intermediate: apical cells broad and rounded at tip, not tending to collapse, rather variable in length but mostly longer than the normal chloridoid type). Microhair apical cell wall thinner than that of the basal cell but not tending to collapse. Microhairs (15–)18–21 microns long; 5.4–6.9 microns wide at the septum. Microhair total length/width at septum 2.2–3.3. Microhair apical cells 9–12 microns long. Microhair apical cell/total length ratio 0.57–0.67. Stomata common; 19.5–21.6 microns long. Subsidiaries mostly low triangular (with small points), or dome-shaped (a few). Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common (in some regions, rare or missing in others); in cork/silica-cell pairs; silicified. Intercostal silica bodies imperfectly developed; cross-shaped (perfect to imperfect). Costal short-cells conspicuously in long rows. Costal silica bodies present in alternate cell files of the costal zones; panicoid-type; large dumb-bell shaped; 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 abaxially only. PCR sheath extensions absent. PCR cell chloroplasts centripetal. Mesophyll traversed by columns of colourless mesophyll cells (in places, but most of the columns fall short of the abaxial surface). Leaf blade adaxially flat. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups (between each pair of bundles); associated with colourless mesophyll cells to form deeply-penetrating fans (mostly, the groups large, linked with colourless columns which sometimes reach the abaxial epidermis), or in simple fans (a few of these, with large, deeply penetrating median cells). 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.
Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Cynodonteae; Gymnopogoninae. 2 species.
Distribution, phytogeography, ecology. Southern tropical and southern Africa.
Helophytic, or mesophytic (open grassland or streamsides); shade species (L. parva), or species of open habitats (L. digitata); glycophytic.
References, etc. Leaf anatomical: studied by us - L. digitata Stapf; photos of L. digitata provided by R.P. Ellis.
Illustrations. • L. digitata: Hook. Ic. Pl. 27 (1901). • General aspect (L. digitata): Gibbs Russell et al., 1990. • L. digitata, abaxial epidermis of leaf blade: this project. • L. digitata, leaf blade TS: 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’.