The grass genera of the world
Habit, vegetative morphology. Annual, or perennial (with slender culms); caespitose, or decumbent. Culms 2–90 cm high; herbaceous; branched above, or unbranched above. Culm nodes hairy. Culm internodes hollow. Plants unarmed. Young shoots intravaginal. Leaves not basally aggregated; non-auriculate. Leaf blades linear-lanceolate to lanceolate; narrow; 2–6 mm wide (the base rounded or contracted); without cross venation. Ligule a fringe of hairs; 0.3 mm long.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate; open, or contracted; with capillary branchlets; espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary, or paired; not secund; pedicellate; consistently in long-and-short combinations, or not in distinct long-and-short combinations; when long-and-short unequally pedicellate in each combination.
Female-fertile spikelets. Spikelets 2.5–6 mm long; brown; compressed laterally to not noticeably compressed; disarticulating above the glumes; disarticulating between the florets (disarticulating readily between L1 and L2, less readily between G2 and L1); with conventional internode spacings. Rachilla terminated by a female-fertile floret; hairless. Hairy callus present. Callus short; blunt.
Glumes two; relatively large; very unequal (G1 one third to one half spikelet length); (the upper) about equalling the spikelets; (the upper) long relative to the adjacent lemmas; hairy, or hairless; pointed (G1 rarely obtuse); awnless (though the G1 can be aristulate and the G2 acuminate); non-carinate; similar (membranous or papery, G1 narrower). Lower glume shorter than the lowest lemma; 3 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; paleate. Palea of the proximal incomplete florets fully developed (two keeled, thin). The proximal incomplete florets male, or sterile. The proximal lemmas awnless; (1–)3 nerved; decidedly exceeding the female-fertile lemmas; less firm than the female-fertile lemmas to similar in texture to the female-fertile lemmas; not becoming indurated (resembling the G2 in form and texture).
Female-fertile florets 1. Lemmas similar in texture to the glumes to decidedly firmer than the glumes (membranous, hardening to leathery); incised; 2 lobed; deeply cleft; awned. Awns 1, or 3; median, or median and lateral (with the lobes terminating in awns additional to the median); the median different in form from the laterals (when laterals present); from a sinus; geniculate; hairless; much longer than the body of the lemma; entered by one vein; persistent. The lateral awns when present, shorter than the median (straight). Lemmas hairy. The hairs in tufts (with a sub-marginal tuft of erect hairs, in the middle on each side). Lemmas non-carinate; having the margins inrolled against the palea (the palea embraced and almost enclosed); without a germination flap; 5–7 nerved; with the nerves non-confluent. Palea present; relatively long; minutely apically notched; awnless, without apical setae; not indurated (hyaline); 2-nerved; 2-keeled. Palea keels wingless. Lodicules present; 2; free; fleshy. Stamens 2. Anthers about 1 mm long; not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2; white.
Fruit, embryo and seedling. Fruit longitudinally grooved. Hilum long-linear. Embryo large.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (the costals narrower and more regularly rectangular in T. stolziana and T. dregeana); differing markedly in wall thickness costally and intercostally (the costals thinner walled). Mid-intercostal long-cells rectangular and fusiform; having markedly sinuous walls. Microhairs present; panicoid-type; (36–)39–42(–45) microns long; (5.1–)5.7–6(–6.6) microns wide at the septum. Microhair total length/width at septum 5.9–8.2. Microhair apical cells 21–25.5(–28.5) microns long. Microhair apical cell/total length ratio 0.54–0.68. Stomata common; 31–36 microns long. Subsidiaries triangular, or dome-shaped and triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common (sometimes paired with macrohair bases); not silicified. Costal zones with short-cells. Costal short-cells conspicuously in long rows. Costal silica bodies panicoid-type; mostly dumb-bell shaped; not sharp-pointed.
Transverse section of leaf blade, physiology. C4. The anatomical organization conventional, or unconventional. Organization of PCR tissue when unconventional Arundinella type. XyMS. PCR sheath outlines uneven. PCR cell chloroplasts centrifugal/peripheral. Mesophyll exhibiting circular cells, or without circular cells. Leaf blade adaxially flat. Midrib not readily distinguishable (at least in the two species seen); with one bundle only. Bulliforms present in discrete, regular adaxial groups, or not present in discrete, regular adaxial groups (T. stolziana having a largely, irregularly bulliform epidermis). Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present, or absent (T. stolziana with little sclerenchyma, as strands only); when present, forming figures. Sclerenchyma all associated with vascular bundles.
Cytology. Chromosome base number, x = 12 (?). 2n = 24. 2 ploid (?).
Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Arundinelleae. Soreng et al. (2015): Panicoideae; Tristachyideae. 5 species.
Distribution, phytogeography, ecology. Southern and tropical Africa, Madagascar.
Helophytic, or mesophytic; shade species, or species of open habitats; glycophytic. Streambanks, grasslands and forest margins.
References, etc. Leaf anatomical: Metcalfe 1960; studied by us - T.x stolziana Henrard; photos of T. dregeana provided by R.P. Ellis.
Illustrations. • T. dregeana: Wood, Natal Plants 2 (1899). • General aspect (T. dregeana): Gibbs Russell et al., 1990. • T. stolziana, 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: 11th December 2017. delta-intkey.com/grass’.