Stiburus Stapf
Sometimes referred to Eragrostis
Habit, vegetative morphology. Annual; caespitose. Culms 10–63 cm high; herbaceous; unbranched above. Plants unarmed. Young shoots intravaginal. Leaves mostly basal; non-auriculate. Leaf blades narrow; setaceous (in the upper part), or not setaceous (but narrow); exhibiting multicellular glands abaxially (at the base of macrohairs). The abaxial leaf blade glands intercostal. Leaf blades without cross venation; persistent; a fringed membrane (very narrow), or a fringe of hairs; ligule very short.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate; contracted; spicate (purplish); non-digitate; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets 4 mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairless (save at the nodes); the rachilla extension with incomplete florets. Hairy callus present (but minute). Callus short.
Glumes two; very unequal to more or less equal; shorter than the adjacent lemmas, or long relative to the adjacent lemmas; hairy (with abundant tubercle based hairs); pointed (acute or acuminate); awnless; carinate; similar. Lower glume longer than half length of lowest lemma; 1 nerved. Upper glume 1 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped. Spikelets without proximal incomplete florets.
Female-fertile florets 1–5. Lemmas similar in texture to the glumes (thin); not becoming indurated; entire; pointed; mucronate (excurrent into the mucro); hairy; carinate, or non-carinate (S. conrathii); without a germination flap; 3 nerved. Palea present; relatively long, or conspicuous but relatively short; entire; awnless, without apical setae; not indurated (thin); 2-nerved; 2-keeled. Lodicules present; 2; free; fleshy (tiny); glabrous; not or scarcely vascularized. Stamens 3. Anthers minute; not penicillate; without an apically prolonged connective. Ovary glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small (about 2 mm long); not noticeably compressed. Hilum short. Pericarp fused (probably).
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 (and pitted). Microhairs absent. Stomata common; 16–21 microns long. Subsidiaries dome-shaped. Guard-cells overlapped by the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs and not paired (some solitary); silicified (sometimes). Intercostal silica bodies absent. With abundant large cushion based macrohairs. Costal short-cells conspicuously in long rows. Costal silica bodies present in alternate cell files of the costal zones; ‘panicoid-type’; cross shaped, or dumb-bell shaped (mostly two-lobed); not sharp-pointed.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+ (the ms cells very large, larger than the PCR cells, with very thick walls). PCR sheaths of the primary vascular bundles interrupted; interrupted both abaxially and adaxially. PCR sheath extensions absent. PCR cell chloroplasts centrifugal/peripheral. Mesophyll traversed by columns of colourless mesophyll cells (very wide columns, cf. Aristida). Leaf blade with distinct, prominent adaxial ribs to ‘nodular’ in section; with the ribs more or less constant in size (primary bundles in bigger ribs). Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups; associated with colourless mesophyll cells to form deeply-penetrating fans (these linked with the wide traversing columns of colourless cells). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all bundles - the fibre groups interrupting the PCR sheath); forming ‘figures’. Sclerenchyma all associated with vascular bundles. The lamina margins with fibres.
Taxonomy. Chloridoideae; main chloridoid assemblage.
Distribution, ecology, phytogeography. 2 species; southern Africa.
Paleotropical. African. Sudano-Angolan. South Tropical African.
References, etc. Leaf anatomical: this project.
Illustrations. • General aspect. • 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).
