The grass genera of the world
Including Aelbroeckia De Moor, Chamaedactylis T. Nees
Habit, vegetative morphology. Perennial; rhizomatous, or stoloniferous, or caespitose, or decumbent. Culms 5–40 cm high; herbaceous; branched above, or unbranched above. Leaves not basally aggregated; non-auriculate. Leaf blades linear to linear-lanceolate (with a cartilaginous, often pungent apex); narrow; 0.6–3 mm wide; flat, or folded; without abaxial multicellular glands; without cross venation. Ligule a fringed membrane to a fringe of hairs.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence a single spike (ovoid to capitate), or of spicate main branches (then a 2-sided raceme of short, densely spiculate sessile spikes appressed to the main axis); espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; secund.
Female-fertile spikelets. Spikelets 2.2–5 mm long; compressed laterally; disarticulating above the glumes. Rachilla prolonged beyond the uppermost female-fertile floret; hairless. Hairy callus absent. Callus short; blunt.
Glumes two; very unequal; shorter than the spikelets; shorter than the adjacent lemmas; lateral to the rachis; awnless; carinate; similar (membranous to leathery). Lower glume 1–3 nerved. Upper glume 5–7 nerved. Spikelets without proximal incomplete florets.
Female-fertile florets 4–18. Lemmas similar in texture to the glumes; not becoming indurated; entire, or incised; when incised, not deeply cleft (emarginate); mucronate; hairy; carinate; 9–11 nerved. Palea present; relatively long; entire to apically notched; awnless, without apical setae; not indurated (membranous); 2-nerved. Lodicules present; 2; free; fleshy; ciliate, or glabrous. Stamens 3. Anthers 0.8–1.6 mm long; not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea; ellipsoid; compressed dorsiventrally. Hilum short. Pericarp fused. Embryo large; not waisted. Endosperm hard; without lipid; containing compound starch grains. 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 present (very abundant, large, thick walled); costal and intercostal. Intercostal papillae over-arching the stomata (so as to thoroughly obscure them); consisting of one oblique swelling per cell, or consisting of one symmetrical projection per cell. Long-cells markedly different in shape costally and intercostally (the costals conventionally shaped); of similar wall thickness costally and intercostally (quite thick walled). Intercostal zones exhibiting many atypical long-cells (all being relatively short). Mid-intercostal long-cells rectangular (to irregular); having markedly sinuous walls. Microhairs present; more or less spherical, or elongated; clearly two-celled; chloridoid-type. Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhairs 21–27 microns long. Microhair basal cells 9 microns long. Microhairs 13.5–18 microns wide at the septum. Microhair total length/width at septum 1.5–2. Microhair apical cells 14–18 microns long. Microhair apical cell/total length ratio 0.55–0.69. Stomata common (but almost invisible). Subsidiaries non-papillate; triangular. Intercostal short-cells common; hard to observe, but seemingly solitary, paired and even in short rows; not silicified. Intercostal silica bodies absent. Costal short-cells conspicuously in long rows. Costal silica bodies present in alternate cell files of the costal zones; panicoid-type; mostly short butterfly shaped to dumb-bell shaped (a few almost square).
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 complete to interrupted; interrupted abaxially only. PCR sheath extensions absent. PCR cell chloroplasts centripetal. Mesophyll with radiate chlorenchyma; traversed by columns of colourless mesophyll cells (at least in places). Leaf blade with distinct, prominent adaxial ribs; 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 simple fans, or associated with colourless mesophyll cells to form deeply-penetrating fans (sometimes associated with colourless girders). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming figures. Sclerenchyma all associated with vascular bundles. The lamina margins with fibres.
Cytology. Chromosome base number, x = 10. 2n = 20. 2 ploid. Chromosomes small.
Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Cynodonteae; Aeluropodinae. 5 species.
Distribution, phytogeography, ecology. Mediterranean to India.
Species of open habitats; halophytic. In sand of seashores and deserts.
Rusts and smuts. Rusts Puccinia. Smuts from Ustilaginaceae. Ustilaginaceae Sorosporium and Sphacelotheca.
References, etc. Leaf anatomical: Metcalfe 1960; this project.
Illustrations. • A. lagopoides: Fl. Iraq, 1968
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’.