The grass genera of the world
Habit, vegetative morphology. Coarse, robust perennial; caespitose. Culms 200–400 cm high; herbaceous; to almost 1 cm in diameter. Culm leaves present. Culm internodes solid. Leaves not basally aggregated; non-auriculate. Leaf blades linear, or linear-lanceolate; broad to narrow; 7–15 mm wide (or more); flat (long); without cross venation; persistent. Ligule a fringed membrane; 0.2–0.5 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, or all alike in sexuality (the pedicellate member hermaphrodite, male, female, sterile or vestigial, increasingly reduced towards the raceme tips); hermaphrodite, or hermaphrodite and female-only, or hermaphrodite, female-only, and male-only, or hermaphrodite, female-only, and sterile, or hermaphrodite, female-only, male-only, and sterile. The male and female-fertile spikelets (when both represented) mixed in the inflorescence. The spikelets overtly heteromorphic to homomorphic; in both homogamous and heterogamous combinations, or all in heterogamous combinations.
Inflorescence. Inflorescence of spicate main branches, or paniculate (long, slender, spiciform racemes, borne racemosely on a common axis or some branched); open; subdigitate (the axis sometimes quite short), or non-digitate. Rachides hollowed (to receive the sessile spikelets and the more or less flattened pedicels). Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes spikelike (by appression/embedding of the spikelets and pedicels); the spikelet-bearing axes with more than 10 spikelet-bearing articles. The racemes spikelet bearing to the base. Spikelet-bearing axes clustered (mostly numerous, the occasional one solitary); with substantial rachides; disarticulating; disarticulating at the joints. Articles non-linear (hollowed below, expanded at the apex); with a basal callus-knob; not appendaged; disarticulating transversely; glabrous. Spikelets paired; secund (the racemes somewhat dorsiventral); sessile and pedicellate; imbricate; consistently in long-and-short combinations; in pedicellate/sessile combinations. Pedicels of the pedicellate spikelets free of the rachis (more or less flattened, appressed). The shorter spikelets hermaphrodite. The longer spikelets hermaphrodite, or female-only, or male-only, or sterile.
Female-sterile spikelets. The pedicellate spikelets usually smaller, hermaphrodite or variously reduced (often to female-only rather than male-only in the material seen) or vestigial. Rachilla of male spikelets represented only in J. angolensis, in the specimens seen, prolonged beyond the uppermost male floret. The male spikelets with glumes; with proximal incomplete florets; 1 floreted. The lemmas awnless. Male florets 1; 4 staminate (sic).
Female-fertile spikelets. Spikelets 5–10 mm long; compressed dorsiventrally; planoconvex; falling with the glumes (the sessile spikelets falling with the adjacent joint and pedicel). Rachilla terminated by a female-fertile floret. Hairy callus absent. Callus short (beneath the sessile spikelet); pointed.
Glumes two; very unequal (G1 longer), or more or less equal; exceeding the spikelets; (the longer) long relative to the adjacent lemmas (exceeding them); hairless; scabrous; pointed; awnless; carinate (the upper), or non-carinate (the lower); with the keel conspicuously winged; very dissimilar (G1 dorsally flattened with incurved margins, leathery and much firmer than G2, G2 smaller, naviculate and cartilaginous). Lower glume much exceeding the lowest lemma; two-keeled to not two-keeled (keeled above, incurved below); convex on the back to flattened on the back; not pitted; muricate to prickly (mainly near the margins); 4–6 nerved. Upper glume 3 nerved; prickly (mainly along the keel). Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; paleate, or epaleate (to a scabrous, awnlike structure). Palea of the proximal incomplete florets fully developed, or reduced. The proximal incomplete florets sterile. The proximal lemmas lanceolate, one or two keeled with ciliate margins and scabrous keels; awnless; 2 nerved, or 3 nerved; 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); smooth; not becoming indurated; entire; pointed; awnless; hairy, or hairless (with ciliate margins); carinate. The keel wingless. Lemmas without a germination flap; 3 nerved. Palea present, or absent; when present, relatively long, or conspicuous but relatively short, or very reduced; entire; awnless, without apical setae; textured like the lemma; not indurated; 2-nerved, or nerveless; keel-less. Palea back glabrous, or scabrous. Lodicules present; 2; free; fleshy; glabrous; not or scarcely vascularized. Stamens 3. Anthers 2.5–3.5 mm long; not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases; free. Style bases adjacent. Stigmas 2; red pigmented.
Fruit, embryo and seedling. Fruit compressed dorsiventrally.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells narrower costally; differing markedly in wall thickness costally and intercostally (the costals thicker walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; panicoid-type. Stomata common. Subsidiaries non-papillate; high to medium dome-shaped (mostly), or triangular (a few, slightly). Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; mostly in cork/silica-cell pairs. No macrohairs or prickles seen. Costal zones with short-cells. Costal short-cells predominantly paired, or neither distinctly grouped into long rows nor predominantly paired (the pairs in places supplemented by short rows). Costal silica bodies panicoid-type; shortly dumb-bell shaped.
Transverse section of leaf blade, physiology. C4; XyMS. PCR sheath outlines uneven. PCR sheath extensions absent. Mesophyll with radiate chlorenchyma. Leaf blade with distinct, prominent adaxial ribs; with the ribs very irregular in sizes (mostly low, encompassing more than one bundle). Midrib very conspicuous; having a conventional arc of bundles (these abaxial, with a large median primary, a large primary on each flank, and smaller bundles in between); with colourless mesophyll adaxially (and a narrow, adaxial lignified hypodermal layer). Bulliforms present in discrete, regular adaxial groups (in places, in the furrows), or not present in discrete, regular adaxial groups (in places); in simple fans and associated with colourless mesophyll cells to form deeply-penetrating fans; associating with colourless mesophyll cells to form arches over small vascular bundles (in places). All the vascular bundles accompanied by sclerenchyma (even the tiniest bundles nearly all associated with at least one abaxial fibre). Combined sclerenchyma girders present (with all but the smallest bundles); forming figures (Is and anchors). Sclerenchyma all associated with vascular bundles.
Classification. Watson & Dallwitz (1994): Panicoideae; Andropogonodae; Andropogoneae; Rottboelliinae. Soreng et al. (2015): cf. Panicoideae; Andropogonodae (?); Andropogoneae (?). 3 species.
Distribution, phytogeography, ecology. Tropical Africa.
Helophytic, or mesophytic.
References, etc. Leaf anatomical: this project.
Special comments. Fruit data wanting. Illustrations. • J. gabonensis: Hook. Ic. Pl. 3 (1922). • J. gabonensis, abaxial epidermis 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: 13th November 2017. delta-intkey.com/grass’.