Amphibromus Nees
Type species: A. neesii Steud.
Slender, tufted perennials, sometimes stoloniferous, with culms decumbent and rooting at nodes, or rhizomatous. Leaf-sheath rounded. Ligule membranous. Leaf-blade linear, narrow, flat or inrolled. Culm erect or geniculate at base, occasionally with corm-like swellings at lower nodes. Panicle narrow, loose, elongated; rachis terete and smooth below, becoming angled and scabrid towards apex, branches erect, slender, often flexuous. Spikelets 3-10-flowered, ⚥, or uppermost ♂, solitary at branchlet tips, pedicelled; disarticulation above glumes and between lemmas; rachilla prolonged. Glumes unequal to subequal, submembranous or hyaline, ± keeled; lower shorter, (1)-3-(5)-nerved, upper broader, 3-7-nerved. Lemma > glumes and firmer, rounded, 5-7-nerved, 2-4-toothed or -lobed, lobes aristate to obtuse; awn dorsal, ± geniculate, ± recurved, arising from near midpoint to just below lemma apex. Palea hyaline, 2-keeled, apex bifid. Callus prominent, hairy. Lodicules membranous, glabrous, spathulate to narrow-triangular, sometimes with a lateral lobe. Ovary glabrous, or slightly hairy at apex; styles free. Caryopsis terete; embryo small, to ⅓ length of caryopsis; hilum linear, to ½ length of caryopsis; endosperm solid. Chasmogamous or cleistogamous.
12 spp. of Australia, N.Z. and South America, with 9 spp. endemic to Australia. Indigenous sp. 1, also occurring in Australia.
The Australian spp. were revised by Jacobs, S. W. L. and Lapinpuro, L. Telopea 2: 715-729 (1986), and their treatment is the basis for this account. They referred A. gracilis P.Morris of New South Wales, Victoria and Tasmania to A. fluitans.
Clayton and Renvoize (1986 op. cit. p. 123) treated Amphibromus as a synonym of Northern Hemisphere Helictotrichon, noting that the glabrous ovary in Amphibromus seemed an inadequate basis for generic separation.
