The grass genera of the world
Including Loxostachys Peter
Habit, vegetative morphology. Annual; decumbent. Culms 10–60 cm high; herbaceous; branched above. Culm nodes glabrous. Culm internodes solid. Leaves not basally aggregated; non-auriculate. Leaf blades lanceolate (acuminate); broad; 6–15 mm wide; not cordate, not sagittate (but asymmetrical at the base); flat; pseudopetiolate; cross veined; persistent. Ligule a fringed membrane; 1.8 mm long.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant, or all alike in sexuality; hermaphrodite, or hermaphrodite and male-only, or hermaphrodite and sterile (some variously incomplete).
Inflorescence. Inflorescence of spicate main branches (spiciform racemes); espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets paired, or solitary (via suppression of one of the pair); secund; pedicellate; consistently in long-and-short combinations, or not in distinct long-and-short combinations.
Female-fertile spikelets. Spikelets 4.6 mm long; adaxial; compressed laterally; falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes two; more or less equal (or G1 shorter); long relative to the adjacent lemmas; dorsiventral to the rachis; pointed; awnless; very dissimilar (the lower smooth, the upper gibbous with translucent intercostal glands and often with hooked spines). Lower glume 3 nerved. Upper glume 7 nerved; prickly. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; paleate. Palea of the proximal incomplete florets fully developed. The proximal incomplete florets male, or sterile. The proximal lemmas awnless; 3 nerved; decidedly exceeding the female-fertile lemmas (equalling the spikelet); similar in texture to the female-fertile lemmas; not becoming indurated (chartaceous, with thin margins and a delicate hyaline area at the base, laterally compressed).
Female-fertile florets 1. Lemmas lanceolate; similar in texture to the glumes to decidedly firmer than the glumes (papery); smooth; not becoming indurated; entire; pointed; awnless; hairless (but sometimes with hooked spines); non-carinate (convex on the back); having the margins inrolled against the palea; with a clear germination flap; 3–5 nerved. Palea present; entire; awnless, without apical setae; textured like the lemma; not indurated; 2-nerved. Lodicules present; 2; free; fleshy; glabrous. Stamens 3. Anthers not penicillate. Ovary apically glabrous. Styles fused, or free to their bases. Stigmas 2; red pigmented.
Fruit, embryo and seedling. Fruit small (1.5 mm long); ellipsoid; compressed dorsiventrally (ventrally flattened). Hilum short. Embryo large; waisted. Endosperm hard; without lipid.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells of similar wall thickness costally and intercostally (thin walled). Intercostal zones with typical long-cells (though these rather short and broad). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; panicoid-type; (36–)39–42(–48) microns long; (3.3–)3.9–4.5(–5.4) microns wide at the septum. Microhair total length/width at septum 6.7–11.8. Microhair apical cells 13.5–15–19.5 microns long. Microhair apical cell/total length ratio 0.32–0.42. Stomata common; about 27 microns long. Subsidiaries triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare; not paired (those seen usually solitary); silicified, or not silicified. Costal short-cells conspicuously in long rows. Costal silica bodies panicoid-type; not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with radiate chlorenchyma; Isachne-type. Leaf blade nodular in section; with the ribs more or less constant in size. Midrib conspicuous; with one bundle only; with colourless mesophyll adaxially (associated with the median bundle). Bulliforms present in discrete, regular adaxial groups; in simple fans (these wide, occupying most of the shallow intercostal depressions). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming figures. Sclerenchyma all associated with vascular bundles.
Cytology. 2n = 36.
Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae. Soreng et al. (2015): Panicoideae; Panicodae; Paniceae; Boivinellinae. 6 species.
Distribution, phytogeography, ecology. 5 in Madagascar, 1 pantropical.
Mesophytic; shade species; glycophytic. In forest.
References, etc. Leaf anatomical: this project.
Illustrations. • P. polystachya: Hooker’s Ic. Pl. 31 (1922). • General aspect (P. polystachya): Gibbs Russell et al., 1990. • P. polystachya, abaxial epidermis of 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: 13th November 2017. delta-intkey.com/grass’.