The grass genera of the world
Habit, vegetative morphology. Annual, or perennial (short-lived); culms prostrate or ascending, often very slender. Culms herbaceous; sparsely branched above. The branching simple. Leaf blades without cross venation. Ligule an unfringed membrane; short.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; hermaphrodite and male-only; overtly heteromorphic; all in heterogamous combinations.
Inflorescence. Inflorescence falsely paniculate (with short racemes in numerous axillary, short-peduncled fascicles); spatheate; a complex of partial inflorescences and intervening foliar organs. Spikelet-bearing axes very much reduced (the racemes usually comprising a basal sessile-bisexual/pedicellate-male pair, and a terminal triad of one sessile-bisexual and two pedicellate-male spikelets); solitary (in spatheolate fascicles); with very slender rachides; disarticulating; disarticulating at the joints (the short raceme disarticulating beneath each sessile spikelet). Articles linear; not appendaged; disarticulating transversely. Spikelets unaccompanied by bractiform involucres, not associated with setiform vestigial branches (i.e., no involucral spikelets); in triplets (terminally), or paired (basally); sessile and pedicellate; consistently in long-and-short combinations; in pedicellate/sessile combinations. Pedicels of the pedicellate spikelets free of the rachis. The shorter spikelets hermaphrodite. The longer spikelets male-only.
Female-sterile spikelets. The pedicelled male spikelets longer, the callus narrowly linear to oblong, lacking the palea and sometimes also the lemma.
Female-fertile spikelets. Spikelets compressed dorsiventrally; falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus present (minute, shortly bearded). Callus short; blunt.
Glumes two; more or less equal; long relative to the adjacent lemmas; hairless (glabrous, smooth); awnless; very dissimilar (membranous, the G1 truncate, dorsally subconvex or concave, margins apically inflexed, broadly involute below, the G2 acute, lanceolate, keeled). Lower glume not two-keeled; convex on the back (slightly), or flattened on the back, or concave on the back; not pitted; relatively smooth; 4–7 nerved. Upper glume 3 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.
Female-fertile florets 1. Lemmas stipitate; not becoming indurated; incised; 2 lobed (these minute, pointed); not deeply cleft; awned. Awns 1; median; from a sinus; geniculate; much longer than the body of the lemma. Lemmas non-carinate; without a germination flap; 1 nerved. Palea absent (in material seen). Lodicules present; 2; free; fleshy; glabrous. Ovary apically glabrous. Stigmas 2.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present. Intercostal papillae not over-arching the stomata; several per cell (a single row per long-cell). Mid-intercostal long-cells rectangular; having markedly sinuous walls (thin; remotely sinuous). Microhairs present; panicoid-type; 36–48(–58) microns long; (3.9–)4.5–5.4 microns wide at the septum. Microhair total length/width at septum 6.7–10. Microhair apical cells (10.5–)12–20(–24) microns long. Microhair apical cell/total length ratio 0.29–0.41. Stomata common; 21–24 microns long. Subsidiaries low dome-shaped and triangular (not conspicuously pointed). Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare (infrequent); silicified (a few). Intercostal silica bodies cross-shaped. Costal short-cells conspicuously in long rows (a few solitary). Costal silica bodies panicoid-type; nodular (mostly), or dumb-bell shaped (a few); not sharp-pointed.
Transverse section of leaf blade, physiology. C4 (vascular bundles crowded); XyMS. Mesophyll without fusoids (but often...a (sheath) cell on either side of each vascular bundle projecting into the adjacent mesophyll). Leaf blade adaxially flat. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups to not present in discrete, regular adaxial groups (irregularly grouped, tending to occupy the entire epidermis in parts); in places in simple fans. Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present (in the ribs). Sclerenchyma all associated with vascular bundles.
Culm anatomy. Culm internode bundles in one or two rings (1–2 more or less distinct circles).
Cytology. 2n = 20.
Classification. Watson & Dallwitz (1994): Panicoideae; Andropogonodae; Andropogoneae; Andropogoninae. Soreng et al. (2015): Panicoideae; Andropogonodae; Andropogoneae; Anthistiriinae. 4 species.
Distribution, phytogeography, ecology. India, Ceylon to Thailand.
Species of open habitats. Hillsides and disturbed ground.
Rusts and smuts. Smuts from Ustilaginaceae. Ustilaginaceae Sorosporium.
References, etc. Leaf anatomical: Metcalfe 1960; this project.
Special comments. Fruit data wanting. Illustrations. • P. umbellata, 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: 13th November 2017. delta-intkey.com/grass’.