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The grass genera of the world

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

Stipagrostis Nees

From the Greek stupe (tow, oakum) or stuppeion (fibre) and agrostis (a fodder grass), alluding either to plumose awns or a perceived likeness to Stipa (another grass genus, q.v.).

Including Schistachne Fig. & De Not

Habit, vegetative morphology. Annual (rarely), or perennial; caespitose. Culms 10–200 cm high; herbaceous; sparsely to amply branched above, or unbranched above. The branching suffrutescent, or simple, or fastigiate. Culm nodes hairy, or glabrous. Culm internodes solid, or hollow. Plants unarmed. Leaves mostly basal, or not basally aggregated. Leaf blades narrowly linear; narrow; setaceous, or not setaceous; flat (rarely), or folded, or rolled (or subterete); not pseudopetiolate; without cross venation; disarticulating from the sheaths, or persistent; once-folded in bud. Ligule a fringe of hairs.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.

Inflorescence. Inflorescence paniculate; open, or contracted; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; not secund; pedicellate.

Female-fertile spikelets. Spikelets 7–20 mm long (?); compressed laterally to not noticeably compressed; disarticulating above the glumes. Rachilla terminated by a female-fertile floret. Hairy callus present, or absent. Callus long (well developed, bearded or not); pointed (rarely rounded or minutely bifid).

Glumes two; very unequal to more or less equal; (the longer) long relative to the adjacent lemmas (usually exceeding it); pointed to not pointed (acuminate to obtuse); awnless; non-carinate; similar (scarious). Lower glume usually 3 nerved. Upper glume 3(–11) nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.

Female-fertile florets 1. Lemmas cylindrical; convolute, or not convolute; decidedly firmer than the glumes (leathery, the glumes membranous); becoming indurated; not deeply cleft; awned. Awns usually triple or trifid, commonly with a basal column, or not of the triple/trifid, basal column type (S. anomala); apical; non-geniculate (at least, not geniculate in the usual sense); usually long-plumose (at least on the median branch), or hairless (S. anomala); much longer than the body of the lemma; entered by several veins (3 veins in the column); deciduous (at the base of the column, or near the middle of the lemma - rarely persistent). Lemmas hairless (usually glabrous or scabrid); non-carinate; with a clear germination flap; 3 nerved. Palea present; conspicuous but relatively short (usually less than half lemma length); entire to apically notched; awnless, without apical setae; thinner than the lemma; indurated; 2-nerved; keel-less. Lodicules present, or absent; when present, 2; free; membranous; glabrous; not toothed; heavily vascularized to not or scarcely vascularized. Stamens 3. Anthers 2–5.5 mm long; 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 (but tightly enclosed in the lemma); fusiform; longitudinally grooved (often, shallowly); compressed dorsiventrally to not noticeably compressed (?). Hilum long-linear. Embryo large; waisted, or not waisted. Endosperm containing compound starch grains. Embryo without an epiblast; with a scutellar tail; with an elongated mesocotyl internode; with one scutellum bundle. Embryonic leaf margins meeting.

First seedling leaf with a well-developed lamina. The lamina narrow; erect; 5 veined.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; panicoid-type; 45–51–57 microns long; 6–7.5 microns wide at the septum. Microhair total length/width at septum 6–8.6. Microhair apical cells 24–28–35 microns long. Microhair apical cell/total length ratio 0.53–0.6. Stomata common; (30–)34.5–45(–48) microns long. Subsidiaries dome-shaped and triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs; silicified. Crown cells present (in the form of numerous bulbous-based and pitted, short pointed or umbonate ‘prickles’). Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies rounded (predominantly, in some species?), or saddle shaped (of the broad, almost round type, predominant in (e.g.) S. ciliata); not sharp-pointed.

Transverse section of leaf blade, physiology. C4; XyMS+ (and PCR sheath single, by contrast with Aristida). Mesophyll traversed by columns of colourless mesophyll cells. Leaf blade with distinct, prominent adaxial ribs to ‘nodular’ in section; with the ribs very irregular in sizes. 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 linking with traversing colourless columns). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with the primaries); forming ‘figures’ (anchors and I’s). Sclerenchyma all associated with vascular bundles.

Phytochemistry. Leaves containing flavonoid sulphates (S. garubensis).

Cytology. Chromosome base number, x = 11. 2n = 22 and 44. 2 and 4 ploid. Chromosomes ‘small’.

Classification. Watson & Dallwitz (1994): Arundinoideae; Aristideae. Soreng et al. (2015): Aristidoideae; Aristideae. 50 species.

Distribution, phytogeography, ecology. Africa, southwest Asia, northwest India.

Xerophytic; species of open habitats. Desert and semidesert, sometimes dunes - e.g. S. ciliata, a sandbinder.

Economic aspects. Cultivated fodder: S. ciliata, S. uniplumis. Important native pasture species: e.g. S. ciliata, S. obtusa, S. plumosa.

References, etc. Morphological/taxonomic: de Winter 1965. Leaf anatomical: studied by us - S. ciliata (Desf.) de Winter, S. uniplumis (Licht.) de Winter.

Illustrations. • General aspect (S. anomala): Gibbs Russell et al., 1990. • General aspect (S. namaquensis): Gibbs Russell et al., 1990. • General aspect, spikelet (S. obtusa): Gibbs Russell et al., 1990. • General aspect (S. zeyheri): Gibbs Russell et al., 1990. • three-branched awn. • S. uniplumis, abaxial epidermis of leaf blade: this project. • S. uniplumis, abaxial epidermis of leaf blade: this project. • S. uniplumis, detail of abaxial epidermis of leaf blade: this project. • S. uniplumis, TS 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.’.