| # The grass genera of the world |

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

### Amphibromus Nees

From the Greek amphi (about, near) and bromos (food, the oat), rightly alluding to similarity with Avena (not Bromus).

~ Helictotrichon

Type species: Type: A. neesii Steud.

Habit, vegetative morphology. Perennial; rhizomatous, or caespitose, or decumbent. Culms 40–180 cm high; herbaceous. Culm nodes glabrous. Culm internodes hollow. Leaves not basally aggregated; non-auriculate. Sheath margins free. Leaf blades apically cucullate, or apically flat; narrow; flat, or rolled (involute); not pseudopetiolate; without cross venation; persistent. Ligule an unfringed membrane; not truncate (elongated, becoming lacerated); 2–15 mm long.

Reproductive organization. Plants bisexual, all 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.

Inflorescence. Inflorescence paniculate; open (narrow, elongated); with capillary branchlets, or without capillary branchlets (often flexuose). Primary inflorescence branches borne distichously. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.

Female-fertile spikelets. Spikelets 7–15 mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets; with conventional internode spacings, or with distinctly elongated rachilla internodes between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairy. Hairy callus present (usually, silky).

Glumes two; more or less equal; shorter than the spikelets; shorter than the adjacent lemmas; pointed, or not pointed; awnless; carinate (slightly), or non-carinate; similar (G2 broader). Lower glume 1–5 nerved. Upper glume 3–7 nerved. Spikelets with female-fertile florets only, or with incomplete florets. The incomplete florets distal to the female-fertile florets (the uppermost male). The distal incomplete florets merely underdeveloped.

Female-fertile florets 2–10. Lemmas 4-toothed or distinctly bifid; decidedly firmer than the glumes; not becoming indurated (firm); incised; 2 lobed, or 4 lobed (toothed); not deeply cleft; awned. Awns 1, or 5; median, or median and lateral; the median different in form from the laterals (when laterals present); dorsal; from well down the back (from about the middle); geniculate; entered by one vein. The lateral awns shorter than the median (straight, terminal). Lemmas hairless; non-carinate; without a germination flap; 3–15 nerved. Palea present; relatively long to conspicuous but relatively short; apically notched (the points acute); awnless, without apical setae; 1-nerved, or 2-nerved, or nerveless; 2-keeled (the keels ciliate), or keel-less. Lodicules present; 2; free; membranous; glabrous; not toothed. Stamens 3. Anthers not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2; white.

Fruit, embryo and seedling. Fruit small; not noticeably compressed. Hilum long-linear. Embryo small; not waisted. Endosperm hard; with lipid; containing compound starch grains.

First seedling leaf with a well-developed lamina.

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; having markedly sinuous walls, or having straight or only gently undulating walls. Microhairs absent. Stomata common. Subsidiaries parallel-sided. Guard-cells overlapped by the interstomatals, or overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies horizontally-elongated crenate/sinuous, or horizontally-elongated smooth, or rounded, or tall-and-narrow.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade; traversed by columns of colourless mesophyll cells. Leaf blade with distinct, prominent adaxial ribs; with the ribs more or less constant in size. Midrib with one bundle only. Bulliforms present in discrete, regular adaxial groups; associated with colourless mesophyll cells to form deeply-penetrating fans (these linked with traversing colourless columns or with abaxial sclerenchyma groups). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders absent. Sclerenchyma not all bundle-associated. The ‘extra’ sclerenchyma in abaxial groups (opposite the furrows); abaxial-hypodermal, the groups continuous with colourless columns.

Phytochemistry. Tissues of the culm bases with little or no starch.

Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Aveneae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Torreyochloinae. 12 species.

Distribution, phytogeography, ecology. Australia, New Zealand, South America.

Helophytic, or mesophytic.

Rusts and smuts. Rusts — Puccinia. Taxonomically wide-ranging species: Puccinia graminis. Smuts from Tilletiaceae. Tilletiaceae — Urocystis.

References, etc. Morphological/taxonomic: Jacobs and Lapinuro 1986. Leaf anatomical: studied by us - Amphibromus ‘sp.’ and A. neesii Steud.

Illustrations. • Amphibromus archeri (as Danthonia): Hooker, Fl. Tasmaniae (1860). • A. nervosus (as Danthonia): Hooker, Fl. Tasmaniae (1860). • Amphibromus neesii, abaxial epidermis of leaf blade: this project. • A. neesii, abaxial epidermis of leaf blade: this project. • Abaxial epidermis of leaf blade (A. neesii). • Amphibromus neesii, TS of leaf blade: this project. • A. neesii, TS 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: 15th June 2025. delta-intkey.com’.

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