The grass genera of the world
Habit, vegetative morphology. Annual; stoloniferous. Culms 15–30 cm high; herbaceous; unbranched above. Culm nodes glabrous. Leaves mostly basal; non-auriculate. The sheaths flattened. Leaf blades narrow; 3–4 mm wide; without abaxial multicellular glands; pseudopetiolate; without cross venation. Ligule a fringed membrane.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence of spicate main branches; digitate. Primary inflorescence branches 2–4. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; subsessile.
Female-fertile spikelets. Spikelets 4.5–5.5 mm long; cuneate; adaxial; compressed laterally; disarticulating above the glumes. Rachilla prolonged beyond the uppermost female-fertile floret (when the L2 has an incomplete floret), or terminated by a female-fertile floret; the rachilla extension when present, with incomplete florets. Hairy callus present. Callus pointed (oblong to linear).
Glumes two; shorter than the spikelets; shorter than the adjacent lemmas; dorsiventral to the rachis; hairless; pointed; awnless; carinate; similar (membranous). Lower glume 1 nerved. Upper glume 1 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.
Female-fertile florets 2 (usually), or 1 (the L2 being sometimes male or sterile). Lemmas decidedly firmer than the glumes (leathery); becoming indurated; incised; 2 lobed; not deeply cleft (bidentate); awned. Awns 1; median; dorsal; from near the top; non-geniculate; hairless (scabrid); much longer than the body of the lemma. Lemmas hairy (pubescent on the back, ciliate near the margins); carinate; prominently 3 nerved (the outer nerves not flanked by wings). Palea present; relatively long; awnless, without apical setae.
Fruit, embryo and seedling. Fruit lanceolate; trigonous. Pericarp fused.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present (in N. humbertiana), or absent (N. perrieri); in N. humbertiana, costal and intercostal (but much more conspicuous intercostally). Intercostal papillae over-arching the stomata (at one end, at least in places); several per cell (small, circular and thick walled, or larger and oblique at the ends of interstomatals). Long-cells similar in shape costally and intercostally to markedly different in shape costally and intercostally (the costals mostly narrower); of similar wall thickness costally and intercostally (of medium thickness). Intercostal zones with typical long-cells. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; more or less spherical to elongated; clearly two-celled; chloridoid-type. Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhair basal cells 6–7 microns long. Microhair total length/width at septum 1.6. Microhair apical cell/total length ratio 0.6. Stomata common. Subsidiaries non-papillate; mostly more or less triangular (in N. perrieri), or dome-shaped and triangular (N. humbertiana). Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common (inconspicuous in N. humbertiana); in cork/silica-cell pairs; silicified (N.perrieri), or not silicified (? N. humbertiana). Intercostal silica bodies imperfectly developed, or present and perfectly developed; rounded and tall-and-narrow (or more or less misshapen, mostly very small). No prickles or macrohairs seen. Costal short-cells conspicuously in long rows. Costal silica bodies present and well developed; present in alternate cell files of the costal zones; very consistently saddle shaped.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+. PCR sheath outlines even (judging from poorly preserved material of N. perrieri), or uneven (judging from poorly preserved material of N. humbertiana). PCR sheaths of the primary vascular bundles interrupted; interrupted both abaxially and adaxially. PCR sheath extensions absent. Leaf blade with distinct, prominent adaxial ribs, or adaxially flat (more or less, in N. humbertiana); with the ribs more or less constant in size. Midrib conspicuous (by the large, rounded abaxial keel, an adaxial bulliform group and conspicuous hinges); with one bundle only; with colourless mesophyll adaxially (N. perrieri), or without colourless mesophyll adaxially (N. humbertiana). The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups, or not present in discrete, regular adaxial groups (the groups, if present, small and indistinct in the material seen); seemingly in simple fans (only). Many of the smallest vascular bundles unaccompanied by sclerenchyma, or all the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming figures (heavy Is with the large bundles in N. perrieri, light ones in N. humbertiana). Sclerenchyma all associated with vascular bundles.
Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae. 3 species.
Distribution, phytogeography, ecology. Madagascar.
Helophytic, or mesophytic; halophytic, or glycophytic. Savanna.
References, etc. Leaf anatomical: this project.
Special comments. Fruit data wanting.
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: 13th November 2017. delta-intkey.com/grass’.