The grass genera of the world
Including Joannegria Chiov., Negria Chiov.
Habit, vegetative morphology. Perennial; caespitose, or rhizomatous and caespitose. Culms 20–90 cm high; herbaceous; branched above. Culm nodes glabrous. Culm internodes hollow. Plants unarmed. Young shoots intravaginal. Leaves not basally aggregated; non-auriculate. Leaf blades linear (tapered to a fine, acuminate tip); narrow; 2–6 mm wide; flat; without abaxial multicellular glands; without cross venation; persistent. Ligule an unfringed membrane (minutely ciliolate, with long hairs at the auricle positions); truncate; 1 mm long. Contra-ligule absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence of spicate main branches; open; digitate, or non-digitate (L. brizoides). Primary inflorescence branches 2–8. Inflorescence espatheate (but often enveloped below by the sheath of the uppermost culm leaf); not comprising partial inflorescences and foliar organs. Spikelet-bearing axes racemes. The racemes without spikelets towards the base. Spikelet-bearing axes sinuous, with very slender rachides; persistent. Spikelets solitary; somewhat secund, or not secund; biseriate, or not two-ranked; subsessile to pedicellate.
Female-fertile spikelets. Spikelets 4–11 mm long; plump, cuneate, or elliptic; adaxial; compressed laterally; disarticulating above the glumes; not disarticulating between the florets (the rachilla tough); with conventional internode spacings. Rachilla prolonged beyond the uppermost female-fertile floret; hairy (below the lowest floret), or hairless (between the upper florets); the rachilla extension with incomplete florets. Hairy callus present (i.e., below the lowermost floret). Callus on the lower floret short; blunt.
Glumes two; very unequal (G1 shorter); shorter than the spikelets; shorter than the adjacent lemmas; free; dorsiventral to the rachis; hairless; glabrous (the keel sometimes scabrous); pointed (the nerve slightly excurrent), or not pointed (slightly notched); awnless (sub-mucronate); carinate (slightly), or non-carinate (rounded on the back); similar (persistent, hyaline-membranous). 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 1–4; merely underdeveloped; shortly awned.
Female-fertile florets 2–4. Lemmas decidedly firmer than the glumes (tough and cartilaginous, at least in part); not becoming indurated; shortly incised; 2 lobed; not deeply cleft (emarginate or 2-toothed); awned. Awns 1; median; dorsal; from near the top; non-geniculate (curved); hairless (scabrid); much shorter than the body of the lemma to about as long as the body of the lemma; entered by one vein. Lemmas hairy (the hairs clavate and apiculate, in 5–6 longitudinal rows on the nerves); non-carinate (abaxially rounded); without a germination flap; 5–9 nerved; with the nerves non-confluent. Palea present; relatively long (about 3/4 the length of the lemma); entire, or apically notched (between the prolonged nerve tips); awnless, without apical setae, or with apical setae (comprising the short scabrid nerve-tips); thinner than the lemma; not indurated (hyaline); 2-nerved; 2-keeled (sharply complanate). Palea keels wingless; hairy (conspicuously ciliate). Lodicules present; 2; free; fleshy (cylindrical rather than cuneate); glabrous. Stamens 3; with free filaments (these attached at the base of the ovary, the androecium and gynoecium being borne on a short stipe between the lodicules). Anthers 1 mm long; not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2; red pigmented (dark purple).
Fruit, embryo and seedling. Fruit free from both lemma and palea; small (1.3–2.2 mm long); ellipsoid; strongly compressed dorsiventrally. Hilum short (elliptical). Pericarp free. Embryo large (about half the length of the fruit); not waisted.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; intercostal. Intercostal papillae over-arching the stomata (at one end); consisting of one symmetrical projection per cell (to almost spherical). Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally (thin walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; more or less spherical; clearly two-celled; chloridoid-type (large, with a relatively short basal cell and a hemispherical distal cell). Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhairs 18–21 microns long. Microhair basal cells 6 microns long. Microhairs (9–)11.4–12(–13.5) microns wide at the septum. Microhair total length/width at septum 1.5–2.2. Microhair apical cells 12–13.5 microns long. Microhair apical cell/total length ratio 0.6–0.75. Stomata common; 22.5–25.5 microns long. Subsidiaries mostly triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare; where detected, not paired. Intercostal silica bodies absent. Crown cells absent (and prickles at leaf margins only). Costal short-cells conspicuously in long rows (but the short-cells sometimes rather long). Costal silica bodies present in alternate cell files of the costal zones; saddle shaped; 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 both abaxially and adaxially. PCR sheath extensions absent. PCR cell chloroplasts centrifugal/peripheral. Mesophyll with radiate chlorenchyma. Midrib conspicuous; having a conventional arc of bundles (large median, and 4 small bundles on each side); with colourless mesophyll adaxially. Bulliforms present in discrete, regular adaxial groups; in simple fans and associated with colourless mesophyll cells to form deeply-penetrating fans (a few of the latter only, with small internal colourless cells). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with the primaries); forming figures. Sclerenchyma all associated with vascular bundles. The lamina margins with fibres.
Cytology. 2n = 30.
Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Cynodonteae; Eleusininae. 2 species.
Distribution, phytogeography, ecology. Tropical east Africa.
Helophytic, or mesophytic; shade species, or species of open habitats; glycophytic. Savanna, heavy soils in seasonally wet places.
References, etc. Leaf anatomical: studied by us - L. nutans Stapf; photos of L. nutans provided by R.P. Ellis.
Illustrations. • L. nutans: Hook. Ic. Pl. 30 (1911). • General aspect (L. nutans): Gibbs Russell et al., 1990. • L. nutans, abaxial epidermis of leaf blade: this project. • L. nutans, abaxial epidermis of leaf blade, detail: 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’.