The grass genera of the world
Type species: Type: L. gracile Brongn.
Including Acroelytrum Steud., Allelotheca Steud.
Habit, vegetative morphology. Perennial; caespitose. Culms 50–120 cm high; herbaceous; not tuberous (but L. gracile with root tubers). Culm nodes glabrous. Culm internodes solid, or hollow. Leaves not basally aggregated; non-auriculate; without auricular setae. Leaf blades linear-lanceolate to ovate-lanceolate; broad; not cordate, not sagittate (rather oblique at the base); pseudopetiolate (the pseudopetiole often winged); cross veined; persistent. Ligule present; an unfringed membrane (ciliolate); truncate.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence of spicate main branches, or paniculate (the unilateral racemes solitary to paired on the common axis); open; espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets 8–13 mm long; compressed laterally (to sub-terete); falling with the glumes; not disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairless; the rachilla extension with incomplete florets. Hairy callus absent.
Glumes two; more or less equal; shorter than the adjacent lemmas; free; lower often with tubercle-based hairs submarginally near the apex; not pointed (obtuse); awnless; non-carinate (rounded on the back); membranous with hyaline margins. Lower glume 5 nerved. Upper glume 7 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets (reduced to their recurved, retrorsely-scabrid lemma awns). The distal incomplete florets 3–4(–9); clearly specialised and modified in form (the fan of awns forming an adhering apparatus). Spikelets without proximal incomplete florets.
Female-fertile florets 1. Lemmas not becoming indurated; entire; blunt; awned (the awns retrorsely scabrid). Awns 1; median; apical; non-geniculate; hairless; much shorter than the body of the lemma. Lemmas hairless; glabrous; carinate; strongly 7–13 nerved. Palea present; 2-nerved; strongly 2-keeled. Lodicules present; 2; free; fleshy; glabrous; heavily vascularized. Stamens 2. Anthers not penicillate. Styles fused.
Fruit, embryo and seedling. Embryo with an epiblast; with a scutellar tail; with an elongated mesocotyl internode. Embryonic leaf margins overlapping.
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 (thin walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; panicoid-type; 31–54 microns long; (5.4–)6 microns wide at the septum. Microhair total length/width at septum 8.2–9. Microhair apical cells (18–)22–30 microns long. Microhair apical cell/total length ratio 0.5–0.6. Stomata common; (33–)36–42(–45) microns long. Subsidiaries triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs (usually), or not paired (some solitary); silicified. Intercostal silica bodies cross-shaped, or vertically elongated-nodular. Costal short-cells conspicuously in long rows. Costal silica bodies panicoid-type; dumb-bell shaped; not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with adaxial palisade (at least over the bundles); without arm cells; with fusoids (in the form of short, lateral PBS extensions, c.f. Orthoclada, Centotheca etc.). The fusoids an integral part of the PBS. Leaf blade adaxially flat. Midrib conspicuous; with one bundle only. Bulliforms not present in discrete, regular adaxial groups (much of the intercostal epidermis irregularly bulliform). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming figures. Sclerenchyma all associated with vascular bundles.
Cytology. Chromosome base number, x = 12. 2n = 48. 4 ploid.
Classification. Watson & Dallwitz (1994): Centothecoideae; Centotheceae. Soreng et al. (2015): Panicoideae; Zeugiteae. 2 species.
Distribution, phytogeography, ecology. Eastern Asia, Indomalayan region, tropical Australia.
Shade species to species of open habitats.
Rusts and smuts. Rusts Puccinia.
References, etc. Leaf anatomical: Metcalfe 1960 and this project.
Special comments. Fruit data wanting. Illustrations. • L. gracile: Hsu (1975), Taiwan Grasses. • L. gracile, abaxial epidermis of leaf blade: this project. • L. gracile, 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: 13th November 2017. delta-intkey.com/grass’.