The grass genera of the world
Type species: Type: P. nervilemma B.K. Simon.
Habit, vegetative morphology. Erect annual. Culms 12–40 cm high; herbaceous; unbranched above; 1–3 noded (terete). Leaves not basally aggregated; non-auriculate. Sheaths hispid, with tubercle based hairs. Leaf blades linear (hispid); narrow; 1–4 mm wide (to 10 cm long); flat, or folded; without abaxial multicellular glands; without cross venation; persistent. Ligule a fringed membrane; 0.2–0.3 mm long.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate; contracted to open; when contracted, more or less irregular; espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate (the pedicels 0.5–1 mm long, hairy).
Female-fertile spikelets. Spikelets 5–11 mm long (3–6 mm wide); strongly compressed laterally; disarticulating above the glumes (but the glumes falling later); not disarticulating between the florets (the rachilla rigid). Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Hairy callus absent. Callus short.
Glumes two; very unequal; shorter than the spikelets; shorter than the adjacent lemmas; hairless; scaberulous on the margins and keel; pointed; awnless; carinate; similar (lanceolate, acuminate, usually mauve). Lower glume 1 nerved. Upper glume 3 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets awned. Spikelets without proximal incomplete florets.
Female-fertile florets 2–8. Lemmas rigid, flattened, yellowish green or the apices infused with mauve, dark-pigmented on the lateral nerves; similar in texture to the glumes (leathery); not becoming indurated; entire; pointed; awnless (acute to acuminate), or awned (the awns increasingly emphasized acropetally in the spikelet). Awns 1; median; apical; non-geniculate; hairless (scabrous); much shorter than the body of the lemma to about as long as the body of the lemma; persistent. Lemmas hairless; scaberulous on the keel and margins; carinate; without a germination flap; 5 nerved, or 7 nerved (the laterals more or less grouped together). Palea present; conspicuous but relatively short (about half the lemma length, comma shaped); awnless, without apical setae; hyaline, with leathery and scaberulous margins; not indurated; 2-nerved; 2-keeled. Palea keels winged; scabrous. Lodicules present; 2; free; fleshy; glabrous. Stamens 3. Anthers about 0.5 mm long (mauvish red). Ovary apically glabrous. Stigmas 2; pale yellow, plumose.
Fruit, embryo and seedling. Fruit small (about 1.4 mm long); ellipsoid; slightly compressed laterally, or not noticeably compressed. Hilum short. Pericarp fused. Embryo large (about half the length of the caryopsis).
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (the costals smaller and narrower); of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; panicoid-type. Microhair apical cell wall thinner than that of the basal cell and often collapsed. Microhair basal cells 21 microns long. Microhair total length/width at septum 5. Microhair apical cell/total length ratio 0.5. Stomata common. Subsidiaries triangular (predominantly), or dome-shaped. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs (a few only, with crescentic silica bodies), or not paired (mostly solitary and unsilicified); mostly not silicified. Intercostal silica bodies absent, or imperfectly developed. Costal short-cells predominantly paired. Costal silica bodies present throughout the costal zones; saddle shaped (a very small version, predominating), or tall-and-narrow to crescentic (intergrading with the saddles); not sharp-pointed.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+. PCR sheath outlines uneven. PCR sheaths of the primary vascular bundles interrupted; interrupted abaxially only. PCR sheath extensions present. Maximum number of extension cells 2–3. Mesophyll with radiate chlorenchyma. Leaf blade with distinct, prominent adaxial ribs; with the ribs more or less constant in size (low). Midrib fairly conspicuous (via a widish, flat abaxial keel and the larger bundle); with one bundle only. The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups (the groups very large, one in each furrow); in simple fans (these predominating, the median cells large and deeply penetrating), or associated with colourless mesophyll cells to form deeply-penetrating fans (these infrequent). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (nearly all the bundles); forming figures (nearly every bundle with an I or an anchor). Sclerenchyma all associated with vascular bundles. The lamina margins with fibres.
Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Eragrostideae; Eragrostidinae. 1 species (P. nervilemma).
Distribution, phytogeography, ecology. Restricted to the Cook pastoral district of northern Qld.
Mesophytic to xerophytic; species of open habitats; glycophytic. In sandy soils.
References, etc. Morphological/taxonomic: Simon 1986. Leaf anatomical: studied by us.
Illustrations. • Spikelet of P. nervilemma. • Lemma of P. nervilemma
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’.