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The grass genera of the world

L. Watson, T.D. Macfarlane, and M.J. Dallwitz

Farrago W. Clayton

Name (= potpourri, hodge-podge) alluding to the ‘morphologically difficult’ spikelets.

Habit, vegetative morphology. Wiry annual; caespitose. Culms 25–50 cm high; herbaceous; to 0.07 cm in diameter; unbranched above. Culm nodes glabrous. Plants unarmed. Leaves not basally aggregated; non-auriculate. Leaf blades linear (acuminate); narrow; about 1.5 mm wide (and 3–8 cm long, glabrous); setaceous, or not setaceous; without abaxial multicellular glands; not pseudopetiolate; without cross venation; persistent. Ligule a fringe of hairs. Contra-ligule absent.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; hermaphrodite and sterile (the basal spikelet of the triplet reduced to a long-aristate glume, the middle one fertile, the upper reduced to a linear, long-aristate glume).

Inflorescence. Inflorescence a false spike, with spikelets on contracted axes (a ‘pseudo-raceme’); espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes very much reduced (to glomerules); disarticulating; falling entire (the glomerules falling). Spikelets with ‘involucres’ of ‘bristles’ (these constituted by the basal sterile spikelets). The ‘bristles’ deciduous with the spikelets (?). Spikelets in triplets; secund (the glomerules in two ranks on one side); sessile and pedicellate; consistently in ‘long-and-short’ combinations; in pedicellate/sessile combinations (the sessile, fertile spikelet accompanied by two bristle-like sterile spikelets, the one sessile, the other pedicellate).

Female-fertile spikelets. Spikelets unconventional (the present description and interpretation after Clayton (1967)); 2.5–3.5 mm long; compressed dorsiventrally; falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus present (at the bases of the glomerule and of each spikelet).

Glumes two; more or less equal; exceeding the spikelets; long relative to the adjacent lemmas (much exceeding them); (the lower) awned (with an 8 mm scabrid awn); carinate; very dissimilar (membranous - G1 asymmetric, ciliate-keeled, long-aristate, G2 symmetrical, scabridulous, shortly aristulate). Lower glume 1 nerved. Upper glume 1 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.

Female-fertile florets 1. Lemmas only about 2 mm long; less firm than the glumes (hyaline); not becoming indurated; entire; blunt; awnless; hairy (dorsally pilose above); 0 nerved. Palea present; conspicuous but relatively short (about half the lemma length); entire; awnless, without apical setae; not indurated; nerveless; keel-less. Lodicules present; 2; free; glabrous; not or scarcely vascularized. Stamens 3. Anthers not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles basally fused. Stigmas 2.

Fruit, embryo and seedling. Fruit small (1.6 mm long); ellipsoid; compressed dorsiventrally. Hilum short (?). Pericarp fused. Embryo large (?); with an epiblast; with a scutellar tail; with an elongated mesocotyl internode; with one scutellum bundle. Embryonic leaf margins meeting.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Microhairs present; elongated; clearly two-celled; chloridoid-type. Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhair basal cells 12 microns long. Microhair total length/width at septum 3. Microhair apical cell/total length ratio 0.5. Stomata common. Subsidiaries triangular. 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 dumb-bell shaped.

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. PCR sheath extensions absent. Mesophyll with radiate chlorenchyma. Leaf blade with distinct, prominent adaxial ribs. Midrib conspicuous; with one bundle only. Bulliforms present in discrete, regular adaxial groups. All the vascular bundles accompanied by sclerenchyma. Sclerenchyma all associated with vascular bundles. The lamina margins without fibres.

Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Cynodonteae; Farragininae. 1 species (F. racemosa).

Distribution, phytogeography, ecology. Tanzania.

Xerophytic; species of open habitats. Rock crevices.

References, etc. Morphological/taxonomic: Clayton 1968. Leaf anatomical: Van den Borre 1994.

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.’.