The grass genera of the world
Habit, vegetative morphology. Perennial; caespitose. Culms 30–90 cm high; herbaceous; unbranched above. Culm nodes glabrous. Culm internodes solid. Plants unarmed. Young shoots intravaginal. Leaves mostly basal to not basally aggregated; non-auriculate. Leaf blades linear (tough, glaucous); narrow; usually folded; without abaxial multicellular glands; without cross venation; rolled in bud. Ligule present; a fringed membrane (narrow); truncate; 0.3 mm long. Contra-ligule absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence of spicate main branches (when closely examined, of numerous lateral racemes, these short, imbricate and appressed); contracted (spiciform); non-digitate. Primary inflorescence branches 25–40 (or more?). Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; secund (more or less); subsessile.
Female-fertile spikelets. Spikelets 3–3.5 mm long; adaxial; compressed laterally; disarticulating between the glumes (the G1 persistent, the G2 falling with the florets); not disarticulating between the florets; with conventional internode spacings. Rachilla prolonged beyond the uppermost female-fertile floret; hairless (glabrous); the rachilla extension with incomplete florets. Hairy callus present. Callus short; blunt.
Glumes two; more or less equal; about equalling the spikelets; long relative to the adjacent lemmas (much longer); lateral to the rachis; hairless (scaberulous); shortly awned (with aristules to 1.5 mm long); non-carinate (rounded on the back); similar (narrowly oblong, membranous, the G1 acute or obtuse, the G2 truncate to emarginate). Lower glume 1 nerved. Upper glume 1 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets 1, or 2 (the second floret male or sterile, the third reduced to an awn); awned. Spikelets without proximal incomplete florets.
Female-fertile florets 1. Lemmas less firm than the glumes to similar in texture to the glumes (thinly membranous); not becoming indurated; entire; pointed; awned. Awns 1; median; apical; non-geniculate; flexuous (slender); hairless (scaberulous); much longer than the body of the lemma. Lemmas hairy (loosely pilose above); non-carinate (rounded on the back); without a germination flap; 3 nerved. Palea present; relatively long; minutely apically notched; awnless, without apical setae (ciliolate); not indurated (hyaline); 2-nerved; 2-keeled (folded). Lodicules present; 2; free; fleshy; glabrous. Stamens 3. Anthers 1–1.5 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 embraced); small (1.3–1.6 mm long); fusiform; compressed dorsiventrally to not noticeably compressed (slightly flattened on the hilar side). Hilum short. Pericarp fused (?). Embryo large.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally (walls of medium thickness). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; chloridoid-type. Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhairs 18–21–22.5 microns long. Microhair basal cells 12 microns long. Microhairs (6.6–)7.5–9(–9.6) microns wide at the septum. Microhair total length/width at septum 2–2.8. Microhair apical cells 6.6–7.5–9 microns long. Microhair apical cell/total length ratio 0.33–0.5. Stomata common; 18–19.5–21 microns long. Subsidiaries mostly dome-shaped (often high). Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; not paired (solitary); not silicified. Intercostal silica bodies absent. Costal short-cells conspicuously in long rows. Costal silica bodies present in alternate cell files of the costal zones; panicoid-type; mostly long to short dumb-bell shaped; not sharp-pointed.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+ (mestome sheath often double, thick-walled). PCR sheaths of the primary vascular bundles interrupted; interrupted abaxially only. PCR sheath extensions absent. Mesophyll traversed by columns of colourless mesophyll cells (probably, though in most bundles the colourless cells fall short of the abaxial epidermis). Leaf blade adaxially flat. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups (very large groups, between all bundles); associated with colourless mesophyll cells to form deeply-penetrating fans (these probably sometimes linked by colourless cells with the abaxial epidermis). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the bundles); forming figures (Is, in all bundles). Sclerenchyma all associated with vascular bundles.
Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae. 1 species (P. greenwayi).
Distribution, phytogeography, ecology. Southern tropical Africa.
Helophytic, or mesophytic (streamsides); glycophytic.
References, etc. Morphological/taxonomic: Hubbard 1940b. Leaf anatomical: studied by us.
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’.