Enneapogon Desv. ex P. Beauv.
From the Greek ennea (nine) and pogon (beard), referring to the nine plumose awn tipped lobes of the lemmas.
Including Calotheria Wight and Arn.
Habit, vegetative morphology. Annual (rarely), or perennial; caespitose. Culms (3–)5–100(–110) cm high; herbaceous. Culm nodes hairy. Culm internodes hollow. Leaves not basally aggregated; auriculate, or non-auriculate. Leaf blades linear; narrow; setaceous, or not setaceous; flat, or rolled (often convolute); without abaxial multicellular glands; not pseudopetiolate; without cross venation; disarticulating from the sheaths, or persistent; rolled in bud; a fringe of hairs.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets; exposed-cleistogamous, or chasmogamous; with hidden cleistogenes, or without hidden cleistogenes. The hidden cleistogenes (when present) in the leaf sheaths (often basal and very modified).
Inflorescence. Inflorescence paniculate; feathery, contracted; capitate, or more or less ovoid, or spicate, or more or less irregular; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; shortly pedicellate.
Female-fertile spikelets. Spikelets 3.5–11 mm long; compressed laterally, or not noticeably compressed, or compressed dorsiventrally; disarticulating above the glumes; not disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairy; the rachilla extension with incomplete florets. Callus short.
Glumes two; very unequal to more or less equal; about equalling the spikelets, or exceeding the spikelets; long relative to the adjacent lemmas; hairy, or hairless; awnless; similar (membranous). Lower glume 5–21 nerved. Upper glume 5–21 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped (sterile or rudimentary), or clearly specialised and modified in form (sometimes reduced to awns and forming a brushlike appendage). Spikelets without proximal incomplete florets.
Female-fertile florets 1–3. Lemmas decidedly firmer than the glumes (firm or leathery); not becoming indurated; incised; usually 9 lobed; deeply cleft (into awns); awned. Awns usually 9; median and lateral; the median similar in form to the laterals; apical; non-geniculate; hairless, or hairy, or long-plumose; about as long as the body of the lemma to much longer than the body of the lemma. The lateral awns about equalling the median. Lemmas villous hairy (with a transverse fringe of hairs inside at base of lobes); non-carinate; 9 nerved (smooth or ribbed). Palea present; relatively long (longer than the body of the lemma); entire (pointed); not indurated (thinly membranous); 2-nerved; 2-keeled (the keels ciliate). Palea keels hairy. Lodicules present; 2; free; fleshy, or membranous; glabrous; not toothed. Stamens 3. Anthers 0.2–1.5 mm long; not penicillate. Ovary glabrous. Styles free to their bases. Stigmas 2; white.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small; compressed dorsiventrally. Hilum short. Pericarp thick and hard; fused. Embryo large; 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 overlapping.
Seedling with a short mesocotyl. First seedling leaf with a well-developed lamina. The lamina narrow.
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 (the costals only slightly thicker walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present (but sometimes rare - e.g., in E. clelandii, where they are, however, abundant on the glumes and lemmas); elongated; clearly two-celled, or clearly two-celled to uniseriate; Enneapogon-type (sometimes up to 8 times the length of an average panicoid-type microhair, and occasionally exhibiting a thin transverse septum in the elongated basal ‘cell’). Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhairs with ‘partitioning membranes’ (in E. nigricans). The ‘partitioning membranes’ in the apical cell. Microhair basal cells 60 microns long. Microhair total length/width at septum 8. Microhair apical cell/total length ratio 0.6. Stomata common. Subsidiaries low dome-shaped, or triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common, or absent or very rare; not paired (when present); 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’; cross shaped to dumb-bell shaped, or nodular (occasionally).
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; biochemical type NAD–ME (in the 7 species typed, although some exhibit ‘PCK-like’ leaf blade anatomy); XyMS+. PCR sheath outlines uneven. PCR sheaths of the primary vascular bundles interrupted; interrupted abaxially only. PCR sheath extensions present. Maximum number of extension cells 1 (usually). PCR cells with a suberised lamella. PCR cell chloroplasts elongated; with well developed grana; centrifugal/peripheral to centripetal. Mesophyll with radiate chlorenchyma; traversed by columns of colourless mesophyll cells. Leaf blade ‘nodular’ in section; with the ribs more or less constant in size. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups; associated with colourless mesophyll cells to form deeply-penetrating fans, or in simple fans and associated with colourless mesophyll cells to form deeply-penetrating fans (often linked with traversing colourless columns). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’. Sclerenchyma all associated with vascular bundles. The lamina margins with fibres.
Culm anatomy. Culm internode bundles in one or two rings.
Phytochemistry. Leaf blade chlorophyll a:b ratio 3.66–4.44.
Special diagnostic feature. Female-fertile lemmas 9-lobed, each lobe terminating in an awn.
Cytology. Chromosome base number, x = 9 and 10. 2n = 18, 36, and 40. 2 and 4 ploid. Chromosomes ‘small’.
Taxonomy. Chloridoideae; Pappophoreae. Nineawn Grasses.
Distribution, ecology, phytogeography. 30 species; in warm regions. Xerophytic; species of open habitats; glycophytic. Bushland and semidesert.
Holarctic, Paleotropical, Neotropical, and Australian. Boreal, Tethyan, and Madrean. African, Madagascan, and Indomalesian. Atlantic North American. Macaronesian, Mediterranean, and Irano-Turanian. Saharo-Sindian, Sudano-Angolan, and Namib-Karoo. Indian, Indo-Chinese, and Papuan. Caribbean. North and East Australian and Central Australian. Central Grasslands. Sahelo-Sudanian, Somalo-Ethiopian, South Tropical African, and Kalaharian. Tropical North and East Australian and Temperate and South-Eastern Australian.
Rusts and smuts. Smuts from Ustilaginaceae. Ustilaginaceae — Sphacelotheca and Ustilago.
Economic importance. Significant weed species: E. cenchroides, E. scoparius. Important native pasture species: several important in dry regions, e.g. E. gracilis, E. nigricans, E. desvauxii.
References, etc. Morphological/taxonomic: Burbidge 1941. Leaf anatomical: Metcalfe 1960; this project.
Illustrations. • General aspect. • General aspect. • Inflorescence. Enneapogon nigricans. • Inflorescence. • Mature inflorescence (detail). • Inflorescence detail. • Inflorescence detail (florets fallen). • Spikelet. Enneapogon nigricans. Two lemmas, each with nine awns. • Spikelet. Enneapogon nigricans. • Awned lemmas. • Spikelet details. • Microhair, abaxial leaf blade epidermis. Enneapogon nigricans. • Microhair, transmission e.m. section
Cite this publication as: Watson, L., and Dallwitz, M. J. (1992 onwards). ‘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.’ http://biodiversity.uno.edu/delta/. Version: 18th August 1999. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993 onwards, 1998), and Watson and Dallwitz (1994), and Watson, Dallwitz, and Johnston (1986) should also be cited (see References).
