Amphibromus Nees
From the Greek amphi (about, near) and bromos (food, the oat), rightly alluding to similarity with Avena (not Bromus).
Sometimes referred to Helictotrichon
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 narrow; flat, or rolled (involute); without cross venation; persistent; an unfringed membrane; not truncate (elongated, becoming lacerated); 2–15 mm long.
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.
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. Spikelets without proximal incomplete florets.
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 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.
Taxonomy. Pooideae; Poodae; Aveneae.
Distribution, ecology, phytogeography. 12 species; Australia, New Zealand, South America. Helophytic, or mesophytic.
Neotropical, Australian, and Antarctic. Central Brazilian, Pampas, and Andean. North and East Australian and South-West Australian. Patagonian. Temperate and South-Eastern Australian.
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: this project.
Illustrations. • General aspect. • Floret. • Abaxial epidermis of leaf blade. • Abaxial epidermis of leaf blade. • Abaxial epidermis of leaf blade. • Transverse section of leaf blade. • Transverse section of leaf blade
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).
