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The grass genera of the world

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

Tarigidia Stent

Habit, vegetative morphology. Glaucous perennial; caespitose. Culms 80–150 cm high; herbaceous; branched above, or unbranched above. Culm nodes glabrous. Culm internodes solid. Plants unarmed. Young shoots intravaginal. Leaves mostly basal (but cauline leaves conspicuous); slightly auriculate, or non-auriculate. The sheath bases sometimes profusely hairy. Leaf blades linear; narrow; 3–6 mm wide; flat (with thickened margins); without cross venation; persistent. Ligule an unfringed membrane; truncate; 1–5 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; hermaphrodite, or hermaphrodite and sterile (in that some at the raceme bases may be sterile).

Inflorescence. Inflorescence a false spike, with spikelets on contracted axes, or paniculate; contracted; spicate (or the lower branches ascending). Inflorescence with axes ending in spikelets, or axes not ending in spikelets (rarely, the lower branches are shortly produced). Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes ‘racemes’ (at the base of the inflorescence), or capitate (at the apex); disarticulating (at least the lower branches do so); falling entire. Spikelets clustered or in pairs on lower panicle branches; secund; shortly pedicellate; imbricate.

Female-fertile spikelets. Spikelets 4–4.5 mm long; abaxial; compressed dorsiventrally; falling with the glumes; not disarticulating between the florets; with conventional internode spacings. Rachilla terminated by a female-fertile floret. Hairy callus absent. Callus absent.

Glumes two; very unequal (the lower sometimes much reduced), or more or less equal (usually); shorter than the spikelets; shorter than the adjacent lemmas; free; hairy (sometimes densely so); pointed (acuminate); awnless; non-carinate. Lower glume shorter than the lowest lemma; 1 nerved. Upper glume 3 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; 5–7 nerved; more or less equalling the female-fertile lemmas; similar in texture to the female-fertile lemmas (papery, with long spreading hairs between nerves and at the margins); not becoming indurated.

Female-fertile florets 1. Lemmas elliptical-obtuse; similar in texture to the glumes; not becoming indurated; entire; pointed; awnless; hairless; non-carinate; having the margins lying flat on the palea; without a germination flap. Palea present; relatively long; tightly clasped by the lemma; entire; awnless, without apical setae; textured like the lemma; not indurated; 2-nerved. Lodicules present; 2; free; fleshy; glabrous; not or scarcely vascularized. Stamens 3. Anthers 2.5 mm long; not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2; red pigmented.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Mid-intercostal long-cells having markedly sinuous walls and having straight or only gently undulating walls (i.e., mixed). Microhairs present; panicoid-type; (69–)78–93(–99) microns long; 4.5–5.1 microns wide at the septum. Microhair total length/width at septum 13.5–20.7. Microhair apical cells (37.5–)42–50(–51) microns long. Microhair apical cell/total length ratio 0.5–0.56. Stomata common; 30–33 microns long. Subsidiaries high dome-shaped (mostly), or triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’; cross shaped to butterfly shaped; not sharp-pointed.

Transverse section of leaf blade, physiology. C4; XyMS–. PCR cell chloroplasts centrifugal/peripheral. Mesophyll with radiate chlorenchyma. Leaf blade adaxially flat. Midrib conspicuous; having a conventional arc of bundles (one large bundle, about 10 small); with colourless mesophyll adaxially. Bulliforms present in discrete, regular adaxial groups; in simple fans. Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders absent. Sclerenchyma all associated with vascular bundles.

Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae. Soreng et al. (2015): Panicoideae; Panicodae; Paniceae; Anthephorinae. 1 species (T. aequiglumis).

Distribution, phytogeography, ecology. Southern Africa.

Mesophytic to xerophytic; species of open habitats; glycophytic. Dry grassland.

Hybrids. A taxon sharing features of Digitaria and Anthephora: originally suggested as an intergeneric hybrid - which accords with absence of fruit in material seen, and the scattered distribution.

References, etc. Morphological/taxonomic: Stent 1932; Loxton 1974. Leaf anatomical: studied by us.

Special comments. Fruit data wanting. Illustrations. • General aspect, spikelet cluster (T. aequiglumis): Gibbs Russell et al., 1990

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.’.