Dregeochloa Conert
In honour of J.F. Drege, a German plant collector in South Africa.
Sometimes referred to Danthonia sensu lato
Habit, vegetative morphology. Perennial; stoloniferous (sometimes), or caespitose (with short, often branched creeping rhizomes). Culms 40–250 cm high; herbaceous; unbranched above (but usually considerably branched just below the soil surface). Culm nodes glabrous. Culm internodes solid. Plants unarmed. Young shoots intravaginal. Leaves mostly basal, or not basally aggregated; non-auriculate. Hair-tufted at the mouth of the sheath. Leaf blades linear, or ovate-lanceolate to ovate; narrow (very rigid); to 3 mm wide; setaceous, or not setaceous; usually folded; not pseudopetiolate; without cross venation; persistent; a fringe of hairs; minute, to 1 mm long.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence few spikeleted (4–12); a single raceme, or paniculate (rarely); when paniculate, contracted (and reduced); espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; not secund; not two-ranked; pedicellate (the rachis and pedicels hairy); not imbricate.
Female-fertile spikelets. Spikelets 10–13 mm long; somewhat compressed laterally; disarticulating above the glumes; disarticulating between the florets; with conventional internode spacings. Rachilla prolonged beyond the uppermost female-fertile floret; hairy, or hairless; the rachilla extension with incomplete florets. Hairy callus present (with a beard on each side). Callus long; pointed.
Glumes two; more or less equal; about equalling the spikelets to exceeding the spikelets; long relative to the adjacent lemmas; minutely hairy, or hairless; when hairless glabrous; pointed (acute); awnless; non-carinate; similar (lanceolate, scarious or herbaceous below, G1 narrower). Lower glume 5 nerved. Upper glume 5–7 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped; awned. Spikelets without proximal incomplete florets.
Female-fertile florets 3–8. Lemmas similar in texture to the glumes (membranous); not becoming indurated; incised; 2 lobed (the lobes acute or bristle-tipped); deeply cleft (to about 1/3); awned. Awns 1; median; from a sinus; geniculate; hairless; about as long as the body of the lemma; entered by one vein; persistent. Lemmas hairy. The hairs in tufts; in transverse rows (the lobes minutely hairy, a row of tufts at their base, and larger marginal tufts beneath). Lemmas non-carinate; 7–9 nerved; with the nerves non-confluent. Palea present; relatively long; entire to apically notched; awnless, without apical setae; thinner than the lemma; not indurated (hyaline); 2-nerved; 2-keeled. Palea keels wingless; hairy. Lodicules present; 2; free; fleshy; glabrous. Stamens 3. Anthers 3 mm long; not penicillate; without an apically prolonged connective. Ovary sparsely hairy. Styles free to their bases. Stigmas 2; red pigmented.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small; longitudinally grooved; compressed dorsiventrally. Hilum short (punctiform). Pericarp thick and hard; free.
Ovule, embryology. Micropyle oblique. Outer integument covering no more than the chalazal half of the ovule; two cells thick at the micropylar margin. Inner integument continuous, the micropyle constricted; thickened around the micropyle. Synergids not haustorial; without large, globular starch grains.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells differing markedly in wall thickness costally and intercostally (the costals very thick-walled). Microhairs present (perhaps?), or absent (apparently, though the hairy grooves are inaccessible: present adaxially); panicoid-type. Stomata hidden. Costal short-cells predominantly paired. Costal silica bodies tall-and-narrow.
Transverse section of leaf blade, physiology. C3 (obviously so in D. pumila, but but the anatomy of D. calvinensis is equivocal, to say the least: most mesophyll cells are no more than one cell distant, and the only seeming exceptions are at the tops of the adaxial ribs. A candidate for intermediacy); XyMS+. Leaf blade with round-topped adaxial ribs, and broad, flat-topped abaxial ribs with deep intercostal furrows; with the ribs more or less constant in size (adaxially). Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups (in the adaxial furrows); in simple fans (but these deeply penetrating in D. pumila). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders absent (the sclerenchyma ‘strands’ in hypodermal bands in the adaxial and abaxial ribs). Sclerenchyma all associated with vascular bundles.
Taxonomy. Arundinoideae; Danthonieae.
Distribution, ecology, phytogeography. 2 species; drier parts of southern Africa. Xerophytic; species of open habitats; halophytic (sometimes), or glycophytic (usually). D. pumila in blown sand over rocks.
Paleotropical and Cape. African. Namib-Karoo.
References, etc. Leaf anatomical: this project; photos of D. pumila provided by R.P. Ellis.
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).