The grass genera of the world
Habit, vegetative morphology. Perennial; caespitose. Culms 30–60 cm high; herbaceous; unbranched above. Plants unarmed. Leaf blades narrow; about 1.5 mm wide (to 25 cm long); rolled; without abaxial multicellular glands; without cross venation. Ligule scarious, long pilose.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence a single spike (14–22 cm long, curved or flexuous). Inflorescence with axes ending in spikelets (?). Spikelet-bearing axes persistent.
Female-fertile spikelets. Spikelets 15 mm long; disarticulating above the glumes. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Hairy callus present (?).
Glumes two; very unequal to more or less equal; (the upper) long relative to the adjacent lemmas; free; hairless; pointed; awnless (but acuminate); similar (divergent, narrowly lanceolate, hyaline). Lower glume 3–5 nerved. Upper glume 3–5 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets several, clustered; awned (male or sterile, and lacking the palea).
Female-fertile florets 1. Lemmas broadly rounded, thinly leathery below, with hyaline lobes; not becoming indurated; incised; 2 lobed; deeply cleft (to below the middle); awned. Awns 1, or 3; median, or median and lateral; the median similar in form to the laterals; from a sinus; non-geniculate; hairy; much longer than the body of the lemma. Lemmas hairy. The hairs in tufts (on the lateral nerves, the lobes glabrous), or not in tufts; not in transverse rows. Lemmas non-carinate (rounded on the back); 3 nerved. Palea present; relatively long; awnless, without apical setae; 2-nerved; 2-keeled. Lodicules present; 2; free; glabrous. Stamens 3. Anthers not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit small (2 mm long); ellipsoid (oblong-elliptical); compressed dorsiventrally. Pericarp free.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; intercostal. Intercostal papillae over-arching the stomata; consisting of one oblique swelling per cell to consisting of one symmetrical projection per cell (the papillae large relative to the cells carrying them). Long-cells differing markedly in wall thickness costally and intercostally (intercostals thicker-walled). Intercostal zones with typical long-cells (but these rather short). Mid-intercostal long-cells rectangular; not readily observable in detail, because of the abundant papillae. Microhairs present; more or less spherical to elongated; clearly two-celled; chloridoid-type. Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhair basal cells 15 microns long. Microhair total length/width at septum 2. Microhair apical cell/total length ratio 0.37. Stomata common. Subsidiaries non-papillate; seemingly all dome-shaped (but extensively obscured by papillae). Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; not paired (solitary); not silicified. Intercostal silica bodies absent. Costal short-cells conspicuously in long rows (but the short-cells rather long in some files). Costal silica bodies present in alternate cell files of the costal zones; exclusively saddle shaped (a rather round form of this type).
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+. PCR sheaths of the primary vascular bundles interrupted; interrupted abaxially only and interrupted both abaxially and adaxially. PCR sheath extensions absent. Mesophyll with radiate chlorenchyma; traversed by columns of colourless mesophyll cells. Leaf blade with distinct, prominent adaxial ribs to nodular in section. Midrib conspicuous (via a rather larger bundle, and its adaxial group of colourless cells); with one bundle only; with colourless mesophyll adaxially. Bulliforms present in discrete, regular adaxial groups; in simple fans, or associated with colourless mesophyll cells to form deeply-penetrating fans (these associated with colourless girders). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with most bundles); forming figures (in the large 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; Eleusininae. 2 species.
Distribution, phytogeography, ecology. Somalia.
References, etc. Leaf anatomical: studied by us - A. martinii Chiov.
Special comments. Fruit data wanting. Illustrations. • A. martinii, 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: 11th December 2017. delta-intkey.com/grass’.