The grass genera of the world

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

Pogonatherum P. Beauv.

From the Greek pogon (beard) and ather (awns on an ‘ear of corn’), referring to the beardlike appearance of inflorescences resulting from fine awns.

Including Homoplitis Trin., Pogonopsis Presl

Habit, vegetative morphology. Delicate perennial; caespitose, or decumbent. Culms 12–60 cm high; branched above. The branching simple, or fastigiate. Culm nodes hairy, or glabrous. Culm internodes solid. Young shoots intravaginal. Leaves not basally aggregated; non-auriculate. Leaf blades narrow; usually flat; pseudopetiolate; without cross venation; persistent. Ligule a fringed membrane.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets (in the sessile spikelets). The spikelets of sexually distinct forms on the same plant; hermaphrodite and female-only (hermaphrodite-sessile and female-pedicelled); more or less homomorphic (the pedicelled slightly smaller).

Inflorescence. Inflorescence a solitary, spicate, pedunculate, axillary ‘raceme’; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes ‘racemes’; solitary; disarticulating; disarticulating at the joints. Spikelets paired; not secund; sessile and pedicellate; consistently in ‘long-and-short’ combinations; in pedicellate/sessile combinations. The ‘shorter’ spikelets hermaphrodite. The ‘longer’ spikelets female-only.

Female-fertile spikelets. Spikelets spikelets small; compressed laterally; falling with the glumes (the pedicelled falling from its pedicel, the sessile falling with the internode and pedicel). Rachilla terminated by a female-fertile floret. Hairy callus present, or absent. Callus blunt.

Glumes two; more or less equal; long relative to the adjacent lemmas; hairy, or hairless; without conspicuous tufts or rows of hairs; (the upper) awned (with a capillary awn from the mid-nerve); very dissimilar (G1 cartilaginous, rounded on the back and truncate, G2 compressed-keeled and awned). Lower glume strongly convex on the back; not pitted; relatively smooth; 0–1 nerved. Upper glume 1 nerved. Spikelets with female-fertile florets only, or with incomplete florets. The incomplete florets proximal to the female-fertile florets. The proximal incomplete florets 1; male, or sterile. The proximal lemmas 0 nerved, or 1 nerved; not becoming indurated.

Female-fertile florets 1. Lemmas less firm than the glumes (thinly membranous to hyaline); not becoming indurated; incised; 2 lobed; deeply cleft to not deeply cleft (to 1/3 to 1/2 its length); awned. Awns 1; median; from a sinus; geniculate; much longer than the body of the lemma (filiform). Lemmas hairless; non-carinate; 1 nerved. Palea present; nerveless. Lodicules absent. Stamens 1–2. Anthers not penicillate. Ovary apically glabrous. Styles fused. Stigmas 2.

Fruit, embryo and seedling. Fruit small; compressed dorsiventrally (flattened on the front). Hilum short. Embryo large.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present. Intercostal papillae over-arching the stomata; several per cell (often slightly irregular in shape). Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; panicoid-type; 24–27(–30) microns long; (3.6–)4.8–5.4 microns wide at the septum. Microhair total length/width at septum 4.4–7.5. Microhair apical cells (10.5–)15–16.5 microns long. Microhair apical cell/total length ratio 0.5–0.63. Stomata common; (18–)21–22.5(–24) microns long. Subsidiaries triangular (or obscured by the papillae). Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare. Costal short-cells conspicuously in long rows. Costal silica bodies acutely-angled (very acutely rectangular); sharp-pointed.

Transverse section of leaf blade, physiology. C4; XyMS–. Mesophyll with radiate chlorenchyma. Leaf blade with distinct, prominent adaxial ribs, or ‘nodular’ in section; with the ribs more or less constant in size. Midrib conspicuous, or not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups (and in irregular groups); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’. Sclerenchyma all associated with vascular bundles.

Cytology. 2n = 20.

Classification. Watson & Dallwitz (1994): Panicoideae; Andropogonodae; Andropogoneae; Andropogoninae. Soreng et al. (2015): Panicoideae; Andropogonodae; Andropogoneae. 3 species.

Distribution, phytogeography, ecology. India to Japan.

Rusts and smuts. Rusts — Puccinia.

References, etc. Leaf anatomical: Metcalfe 1960; studied by us - P. paniceum (Lam.) Hackel.

Illustrations. • P. paniceum, as P. saccharöideum: P. Beauv. (1812). • P. paniceum, 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: 11th December 2017.’.