| # The grass genera of the world |

L. Watson, T.D. Macfarlane, and M.J. Dallwitz

### Ichnanthus P. Beauv.

From the Greek chnos (a footstep or mark), perhaps referring to the appendages beneath the upper floret.

Type species: Type: I. panicoides P.Beauv.

Including Ischnanthus Roem. & Schult., Navicularia Radd.

Habit, vegetative morphology. Annual, or perennial; caespitose, or decumbent. Culms herbaceous; sparsely to amply branched above, or unbranched above. The branching simple. Culm nodes hairy, or glabrous. Culm leaf sheaths rounded. Culm internodes solid, or hollow. Leaves not basally aggregated; non-auriculate. Leaf blades linear to ovate; broad, or narrow; not cordate, not sagittate; pseudopetiolate, or not pseudopetiolate; cross veined, or without cross venation; persistent. Ligule short a fringed membrane, or a fringe of hairs.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality.

Inflorescence. Inflorescence paniculate, or of spicate main branches (the primary branches sometimes unbranched); open; with capillary branchlets. Primary inflorescence branches inserted all around the main axis. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund. Pedicel apices truncate, or cupuliform. Spikelets not in distinct ‘long-and-short’ combinations.

Female-fertile spikelets. Spikelets 4–5 mm long; oblong, or elliptic, or lanceolate, or ovate, or obovate, or oblanceolate; abaxial to adaxial (or not orientated); compressed laterally to compressed dorsiventrally (the L2 dorsally compressed); disarticulating above the glumes, or falling with the glumes; with distinctly elongated rachilla internodes between the florets. The upper floret conspicuously stipitate. The stipe beneath the upper floret not filiform; curved, not swollen (about 1 mm long, bearing a small, white, annular, membranous, minutely two-lobed appendage below the palea); homogeneous. Rachilla terminated by a female-fertile floret. Hairy callus absent.

Glumes two; very unequal (the lower usually about 1/2 to 3/4 of the spikelet length); (the longer) long relative to the adjacent lemmas; pointed; awnless; similar (membranous- herbaceous). Lower glume 0.5–0.75(–1) times the length of the upper glume; 3–7 nerved. Upper glume 5–9 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; paleate. Palea of the proximal incomplete florets fully developed. The proximal incomplete florets male. The proximal lemmas awnless; 5 nerved, or 7 nerved; decidedly exceeding the female-fertile lemmas; less firm than the female-fertile lemmas; not becoming indurated.

Female-fertile florets 1. Lemmas decidedly firmer than the glumes (papery to leathery); smooth; becoming indurated; white in fruit, or yellow in fruit; awnless; hairless; shiny, glabrous; non-carinate; having the margins inrolled against the palea; with a clear germination flap; 5–7 nerved. Palea present; relatively long; tightly clasped by the lemma; entire; awnless, without apical setae; textured like the lemma; indurated; 2-nerved. Lodicules present; 2; free; fleshy; glabrous. Stamens 3. Anthers not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2; red pigmented.

Fruit, embryo and seedling. Disseminule often deciduous before the rest of the spikelet, comprising the fruit and the P2 on the stipe-like rachilla joint, enclosed by the L1. Fruit small; compressed dorsiventrally. Hilum short. Embryo large.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Mid-intercostal long-cells rectangular; having markedly sinuous walls (these very thin). Microhairs present; panicoid-type; 88–92.7 microns long; 5.8–8.8 microns wide at the septum. Microhair total length/width at septum 10–15.4. Microhair apical cells 46.4–53.7 microns long. Microhair apical cell/total length ratio 0.53–0.58. Stomata common (in rows adjoining the veins); 51–70 microns long. Subsidiaries low dome-shaped and triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare (very few); not paired. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’; mostly dumb-bell shaped.

Transverse section of leaf blade, physiology. C3; XyMS+. Leaf blade ‘nodular’ in section. Midrib conspicuous (as a larger bundle and adaxial rib); with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (but most sclerenchyma in strands); forming ‘figures’ (few). Sclerenchyma all associated with vascular bundles.

Phytochemistry. Leaves containing flavonoid sulphates (1 species), or without flavonoid sulphates (1 species).

Cytology. 2n = 18, 20, 40, and 54.

Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae. Soreng et al. (2015): Panicoideae; Panicodae; Paspaleae; Paspalinae. 33 species.

Distribution, phytogeography, ecology. Tropical America, Indomalayan region, Australia.

Mesophytic; shade species and species of open habitats; glycophytic. Forest, grassland and disturbed ground.

Rusts and smuts. Rusts — Puccinia. Taxonomically wide-ranging species: Puccinia levis.

References, etc. Leaf anatomical: studied by us - I. vicinus (F.M. Bailey) Merr.

Illustrations. • Ichnanthus panicoides: Kunth (1835), Dist. méthodique de la famille des Graminées. • Ichnanthus panicoides: P. Beauv. (1812). • Ichnanthus nemorosus, as Panicum: Trinius (1830), Species Graminum. • Ichnanthus nemorosus: Nicora & Rúgolo de Agrasar (1987). • Palea and floret base, S.E.M. (Ichnanthus vicinus). • Ichnanthus australiensis, abaxial epidermis of leaf blade: this project. • Ichnanthus vicinus, abaxial epidermis of leaf blade: 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: 15th June 2025. delta-intkey.com’.

Contents