Prionanthium Desv.
From the Greek prion (saw) and anthos (flower), referring to the serrated lemma keels formed by the glands.
Including Chondrolaena Nees, Prionachne Nees
Habit, vegetative morphology. Slender annual; caespitose. The flowering culms leafless. Culms 4–43 cm high; herbaceous; branched above, or unbranched above. Culm nodes glabrous. Culm internodes hollow. Plants unarmed; with multicellular glands (stalked or sessile, on the glumes of all three species, not on the leaves). Young shoots intravaginal. Leaves not basally aggregated; non-auriculate; without auricular setae (but with a tuft of hairs at the mouth of the sheath). Leaf blades linear (or filiform); narrow; 0.5–2(–3) mm wide (less than 8 cm long); flat, or rolled; without cross venation; persistent; a fringed membrane to a fringe of hairs; 0.3–1.5 mm long. Contra-ligule absent.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence a single spike, or a single raceme (spike-like); contracted (3–8 cm long, the axis curved beside each spikelet); espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary, or paired; secund; biseriate; sessile to subsessile; consistently in ‘long-and-short’ combinations, or not in distinct ‘long-and-short’ combinations.
Female-fertile spikelets. Spikelets 3–7 mm long; adaxial (the upper glume gaping widely at anthesis); compressed laterally; disarticulating above the glumes; disarticulating between the florets (but the disarticulated florets remaining for some time within the persistent glumes). Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension naked.
Glumes two; more or less equal (the lower slightly longer); about equalling the spikelets; long relative to the adjacent lemmas (exceeding them); dorsiventral to the rachis (in P. pholiuroides), or lateral to the rachis; hairy, or hairless (keels and sometimes the nerves tuberculate or pectinate); not pointed (rounded); awnless; carinate (strongly, often asymmetrically); similar (navicular, rigid, leathery with membranous margins enfolding the floret, usually with multicellular glands). Lower glume about equalling the lowest lemma, or much exceeding the lowest lemma; 5–8 nerved. Upper glume 5–8 nerved. Spikelets with female-fertile florets only, or with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped; awnless. Spikelets without proximal incomplete florets.
Female-fertile florets 2. Lemmas acute, lanceolate or lanceolate-oblong; less firm than the glumes; not becoming indurated (thinly membranous); entire; pointed; awnless, or mucronate; hairy, or hairless. The hairs not in tufts (when present, evenly distributed). Lemmas non-carinate (abaxially rounded); without a germination flap; 3–5 nerved. Palea present (sub-linear); relatively long; apically notched; awnless, without apical setae; textured like the lemma; not indurated (hyaline, with thickened keels); 2-nerved; 2-keeled. Lodicules present (minute); 2; free; fleshy; glabrous. Stamens 3. Anthers 1.8–3.9 mm long; not penicillate; without an apically prolonged connective. Ovary glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit narrowly lanceolate in outline; longitudinally grooved. Hilum long-linear. Embryo small. Endosperm containing only simple starch grains.
Ovule, embryology. Micropyle not noticeably oblique. Outer integument covering no more than the chalazal half of the ovule; two cells thick at the micropylar margin. Inner integument discontinuous distally; not thickened around the micropyle. Synergids not haustorial; without large, globular starch grains.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Mid-intercostal long-cells rectangular and fusiform; having markedly sinuous walls. Microhairs present; panicoid-type; (63–)69–75(–81) microns long; 7.5–8.4–10.5 microns wide at the septum. Microhair total length/width at septum 6.9–10. Microhair apical cells 28.5–31.5 microns long. Microhair apical cell/total length ratio 0.38–0.46. Stomata common; 31.5–36 microns long. Subsidiaries parallel-sided to dome-shaped (mostly domes-shaped). Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs (and solitary); silicified. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’; dumb-bell shaped and nodular; not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade. Leaf blade with distinct, prominent adaxial ribs; with the ribs more or less constant in size. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders absent (small abaxial girders only, but with a wide adaxial strand at the top of each rib). Sclerenchyma all associated with vascular bundles.
Cytology. Chromosome base number, x = 7. 2n = 14. 2 ploid (all three species).
Taxonomy. Arundinoideae; Danthonieae.
Distribution, ecology, phytogeography. 3 species; South Africa. Helophytic (in seasonally wet places); species of open habitats; glycophytic.
Cape.
References, etc. Morphological/taxonomic: Davidse, G. (1988). Bothalia 18, 143–153. Leaf anatomical: this project.
Illustrations. • General aspect
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).
