The grass genera of the world
Including Hypudaerus A. Br.
Habit, vegetative morphology. Annual, or perennial; rhizomatous, or caespitose to decumbent. Culms 15–150 cm high; herbaceous; branched above, or unbranched above. Culm nodes glabrous. Culm internodes hollow. Young shoots extravaginal, or intravaginal. Leaves not basally aggregated; non-auriculate. Leaf blades linear to lanceolate; narrow; 1–7 mm wide; not setaceous, or setaceous (when tightly rolled); flat, or rolled; without cross venation; persistent; rolled in bud. Ligule an unfringed membrane, or a fringed membrane; not truncate (often irregularly split almost to the base); 2–8 mm long. Contra-ligule absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant (the involucres of the clusters being here interpreted as modified spikelets, rather than as modified lower glumes of the fertile spikelets); hermaphrodite and sterile, or hermaphrodite and male-only (the glomerules comprising 1–11 central perfect spikelets with two or more outer sterile or male involucral spikelets, the latter mainly manifested as leathery, several nerved bracts); overtly heteromorphic (the involucral spikelets much modified, usually reduced to leathery bracts). Apomictic, or reproducing sexually.
Inflorescence. Inflorescence a false spike, with spikelets on contracted axes (3–11 spikelets per glomerule, the glomerules conical, usually sessile); espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes very much reduced (to glomerules); disarticulating; falling entire (i.e. each glomerule falling from the persistent main axis). Spikelets associated with bractiform involucres (these consisting of the leathery, bractlike vestiges of involucral spikelets, which are sometimes connate at the base). The involucres shed with the fertile spikelets. Spikelets not secund.
Female-sterile spikelets. The outer, involucral spikelets mainly detected as broad, leathery bracts, these 2–15 nerved, sometimes basally connate; the bracts seemingly interpretable as modified lower glumes, being sometimes accompanied by a setaceous G2 and a male floret.
Female-fertile spikelets. Spikelets abaxial (in the sense that the backs of the glumes are to the inside of the glomerule); compressed dorsiventrally; falling with the glumes. Rachilla terminated by a female-fertile floret. Callus absent in the normal sense, but hairs at the base of the glomerule and on the involucre direct the resting position of the glomerule.
Glumes one per spikelet (the upper); long relative to the adjacent lemmas; pointed; awned; non-carinate. Upper glume 1 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; epaleate; sterile. The proximal lemmas awnless; 2–7 nerved; more or less equalling the female-fertile lemmas; less firm than the female-fertile lemmas; not becoming indurated.
Female-fertile florets 1. Lemmas lanceolate; not becoming indurated (membranous); entire; pointed; awnless; hairless; non-carinate; having the margins lying flat on the palea; with a clear germination flap, or without a germination flap; 3–5 nerved. Palea present; relatively long; entire; awnless, without apical setae; textured like the lemma; not indurated; 2-nerved. Lodicules absent. Stamens 3. Ovary apically glabrous. Styles fused, or free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit compressed dorsiventrally. Hilum short. Endosperm hard; without lipid. Embryo without an epiblast; with a scutellar tail; with an elongated mesocotyl internode. Embryonic leaf margins overlapping.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (costals long, narrow, rectangular, intercostals broader, rather variable); of similar wall thickness costally and intercostally (thin walled). Intercostal zones with typical long-cells, or exhibiting many atypical long-cells (e.g. in A. schinzii, which has many of them nearly isodiametric). Mid-intercostal long-cells rectangular, or fusiform; having straight or only gently undulating walls (commonly), or having markedly sinuous walls (e.g. in A. argentea). Microhairs present; panicoid-type; (54–)57–84(–90) microns long; (24–)25–36(–45) microns wide at the septum. Microhair total length/width at septum 9.5–15. Microhair apical cells (3.6–)4.2–6(–9.3) microns long. Microhair apical cell/total length ratio 0.4–0.56. Stomata common; 18–27 microns long. Subsidiaries triangular. Guard-cells overlapped by the interstomatals, or overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare. Costal prickles abundant. Crown cells absent. Costal short-cells conspicuously in long rows, or neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies panicoid-type; cross shaped, or dumb-bell shaped, or nodular.
Transverse section of leaf blade, physiology. C4. The anatomical organization usually conventional, or unconventional (rarely, doubtfully). Organization of PCR tissue when unconventional, supposedly Arundinella type (see W.V. Brown 1977, quoting Johnson 1965). XyMS. PCR sheath outlines even. PCR cell chloroplasts with reduced grana; centrifugal/peripheral. Mesophyll with radiate chlorenchyma; exhibiting circular cells, or without circular cells. Leaf blade with distinct, prominent adaxial ribs, or adaxially flat (but usually with small, conspicuous abaxial ribs). Midrib conspicuous; having a conventional arc of bundles; with colourless mesophyll adaxially. Bulliforms present in discrete, regular adaxial groups, or not present in discrete, regular adaxial groups (e.g. in A. pubescens, where the epidermis is mainly bulliform); in simple fans (when grouped); associating with colourless mesophyll cells to form arches over small vascular bundles, or nowhere involved in bulliform-plus-colourless mesophyll arches. Many of the smallest vascular bundles unaccompanied by sclerenchyma, or all the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present, or absent. Sclerenchyma all associated with vascular bundles.
Culm anatomy. Culm internode bundles in three or more rings.
Phytochemistry. Leaves without flavonoid sulphates (1 species).
Special diagnostic feature. The inflorescence not as in Odontelytrum (q.v.).
Cytology. Chromosome base number, x = 9. 2n = 18, 36, and 40. 2 and 4 ploid.
Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae. Soreng et al. (2015): Panicoideae; Panicodae; Paniceae; Anthephorinae. 12 species.
Distribution, phytogeography, ecology. Tropical and southern Africa, Arabia, tropical America.
Mesophytic to xerophytic; species of open habitats; glycophytic. In dry, sandy savanna.
Rusts and smuts. Rusts Puccinia. Smuts from Ustilaginaceae. Ustilaginaceae Sorosporium and Sphacelotheca.
References, etc. Leaf anatomical: Metcalfe 1960; studied by us - A. acuminata (Rendle) Stapf & Hubbard, A. pubescens Nees; photographs of A. argentea, A. pubescens and A. schinzii provided by R. P. Ellis.
Special comments. Fruit data wanting. Illustrations. • A. pubescens, general aspect: Gibbs Russell et al., 1990. • A. elegans: Fl. Brasiliensis 2 (1877). • A. hermaphrodita, as A. elegans: Lamson-Scribner (1890). • A. acuminata, abaxial epidermis of leaf blade: this project. • A. acuminata, abaxial epidermis of leaf blade: this project. • A. acuminata, transverse section of leaf blade: this project. • A. acuminata, transverse section 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: 11th December 2017. delta-intkey.com/grass’.