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The grass genera of the world

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

Eremochloa Buese

From the Greek eremos (desert) and chloa (grass), referring to habitat.

Including Pectinaria (Benth.) Hack.

Habit, vegetative morphology. Perennial; caespitose. Culm nodes hairy. Culm internodes solid. Young shoots extravaginal. Leaves mostly basal; non-auriculate. Leaf blades narrow; without cross venation; persistent; once-folded in bud. Ligule an unfringed membrane.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; hermaphrodite and sterile; overtly heteromorphic (the ‘pedicelled spikelets’ very reduced); all in heterogamous combinations. Plants outbreeding.

Inflorescence. Inflorescence determinate, or indeterminate; comprising axillary or terminal spike-like, slender flattened ‘racemes’; espatheate; not comprising ‘partial inflorescences’ and foliar organs (or not usually interpreted as such). Spikelet-bearing axes spikelike (exserted on long slender peduncles, curved, with imbricate spikelets); solitary, or paired (rarely); with substantial rachides (these swollen, 3-angled); tardily disarticulating; disarticulating at the joints. ‘Articles’ non-linear (clavate); with a basal callus-knob; densely long-hairy to somewhat hairy. Spikelets paired; secund (the sessile members in two alternating rows, on one side of the rachis); sessile and pedicellate; imbricate; consistently in ‘long-and-short’ combinations; in pedicellate/sessile combinations. Pedicels of the ‘pedicellate’ spikelets free of the rachis (flattened). The ‘shorter’ spikelets hermaphrodite (or those near the tip o sterile). The ‘longer’ spikelets sterile (reduced to a pedicel only, or with rudiments of a spikelet which may take the form of a bristle or mucro).

Female-sterile spikelets. Vestigial.

Female-fertile spikelets. Spikelets compressed dorsiventrally; falling with the glumes (and with the adjacent internode and pedicel). Rachilla terminated by a female-fertile floret. Hairy callus present, or absent.

Glumes two; very unequal; (the longer) long relative to the adjacent lemmas; awnless; very dissimilar (the lower 2-keeled and spiny on the margins, the upper naviculate, smooth, glabrous). Lower glume two-keeled; not pitted; prickly (the lower keels with filiform or flattened scabrid curved or horizontal spines); 5–9 nerved. Upper glume 3 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; paleate; male. The proximal lemmas awnless; more or less equalling the female-fertile lemmas to decidedly exceeding the female-fertile lemmas; similar in texture to the female-fertile lemmas (hyaline); not becoming indurated.

Female-fertile florets 1. Lemmas less firm than the glumes (hyaline); not becoming indurated; entire; pointed; awnless; hairless; non-carinate; 0 nerved. Palea present; textured like the lemma (hyaline); not indurated; nerveless. Lodicules present; 2; free; fleshy; glabrous. Stamens 3. Anthers not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2; red pigmented.

Fruit, embryo and seedling. Fruit small; compressed dorsiventrally. Hilum short. Embryo large. Endosperm containing only simple starch grains. Embryo without an epiblast; with a scutellar tail; with an elongated mesocotyl internode.

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. Mid-intercostal long-cells rectangular (but sometimes with rounded ends); having markedly sinuous walls. Microhairs present; panicoid-type; 53.7–58.6 microns long; 10.7–12.2 microns wide at the septum. Microhair total length/width at septum 4.4–5.5. Microhair apical cells 29–39 microns long. Microhair apical cell/total length ratio 0.55–0.67. Stomata common; 36.6–41.5 microns long. Subsidiaries triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs; silicified. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’.

Transverse section of leaf blade, physiology. C4; XyMS–. PCR sheath outlines uneven. PCR cell chloroplasts with reduced grana; centrifugal/peripheral. Mesophyll with radiate chlorenchyma. Leaf blade adaxially flat. Midrib conspicuous (with a large adaxial bulliform group); having a conventional arc of bundles; with colourless mesophyll adaxially. Bulliforms not present in discrete, regular adaxial groups (the epidermis extensively bulliform). Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’. Sclerenchyma all associated with vascular bundles.

Cytology. Chromosome base number, x = 9. 2n = 18. 2 ploid. Nucleoli persistent.

Classification. Watson & Dallwitz (1994): Panicoideae; Andropogonodae; Andropogoneae; Rottboelliinae. Soreng et al. (2015): Panicoideae; Andropogonodae; Andropogoneae; Rottboelliinae. 9 species.

Distribution, phytogeography, ecology. India, Ceylon, southern China, Southeast Asia, western Malaysia, Australia.

Mesophytic; species of open habitats. Short grassland.

Economic aspects. Lawns and/or playing fields: E. ophiuroides.

Rusts and smuts. Smuts from Ustilaginaceae. Ustilaginaceae — Sorosporium and Sphacelotheca.

References, etc. Leaf anatomical: studied by us - E. bimaculata Hackel.

Illustrations. • E. bimaculata, abaxial epidermis of leaf blade: this project. • E. bimaculata, abaxial epidermis of leaf blade: this project. • E. bimaculata, leaf blade TS: 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.’.