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The grass genera of the world

L. Watson, T.D. Macfarlane, and M.J. Dallwitz

Stiburus Stapf

~ 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. Ligule a fringed membrane (very narrow), or a fringe of hairs; ligule very short.

Reproductive organization. Plants bisexual, all 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.

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 apically 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.

Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Eragrostideae; Eragrostidinae. 2 species.

Distribution, phytogeography, ecology. Southern Africa.

References, etc. Leaf anatomical: studied by us - S. alopecuroides Stapf.

Illustrations. • S. alopececuroides: J.M. Wood (1903), Natal Plants 5 (Grasses). • General aspect (S. alopecuroides): Gibbs Russell et al., 1990. • TS leaf blade of S. alopecuroides: 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.’.