The grass genera of the world
Habit, vegetative morphology. Annual, or perennial; caespitose. Culms branched above. Culm nodes glabrous. Culm internodes hollow. Leaves mostly basal; non-auriculate. Leaf blades very narrow; without cross venation; persistent. Ligule a fringed membrane (short).
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets homomorphic.
Inflorescence. Inflorescence of spicate main branches (having several spike-like racemes on a short axis); open; digitate; espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes racemes (shortly pedunculate); persistent (tough, this being the main distinction from Eulalia), or disarticulating (in some forms); when disarticulating, disarticulating at the joints. Articles glabrous on the back, with villous-ciliate edges. Spikelets paired; not secund; sessile and pedicellate, or subsessile and pedicellate; consistently in long-and-short combinations; in pedicellate/sessile combinations, or unequally pedicellate in each combination. The shorter spikelets hermaphrodite. The longer spikelets hermaphrodite.
Female-fertile spikelets. Spikelets compressed dorsiventrally; falling with the glumes (falling from the pedicels, or persistent on pedicels and internodes). Rachilla terminated by a female-fertile floret. Hairy callus present. Callus blunt.
Glumes present; two; more or less equal; long relative to the adjacent lemmas; without conspicuous tufts or rows of hairs; awned. Lower glume two-keeled, or not two-keeled; convex on the back, or concave on the back (slightly); not pitted; relatively smooth; 2 nerved. Upper glume 1 nerved. Spikelets with female-fertile florets only (the L1 often absent), or with incomplete florets. The incomplete florets (when present) proximal to the female-fertile florets. The proximal incomplete florets (when present) 1; sterile.
Female-fertile florets 1. Lemmas less firm than the glumes; incised; 2 lobed; deeply cleft (bifid), or not deeply cleft (emarginate); awned. Awns 1; median; from a sinus; geniculate; hairy (villous-ciliate at the edges of the column). Lemmas hairless; non-carinate; 0 nerved. Palea present; nerveless. Lodicules present; 2; free; fleshy; glabrous; toothed, or not toothed. Stamens 3. Anthers not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit compressed dorsiventrally to not noticeably compressed. Hilum short. Embryo large.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae dubiousy present, or absent (?). Intercostal papillae if present, several per cell. Long-cells similar in shape costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; panicoid-type; (39–)40.5–45 microns long; 6–6.6–7 microns wide at the septum. Microhair total length/width at septum 5.6–6.8. Microhair apical cells 24–26–27 microns long. Microhair apical cell/total length ratio 0.57–0.65. Stomata common; (21–)22.5–25.5(–27) microns long. Subsidiaries triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; not paired (solitary); not silicified. Costal short-cells conspicuously in long rows. Costal silica bodies panicoid-type; not sharp-pointed.
Transverse section of leaf blade, physiology. C4; XyMS. Mesophyll with radiate chlorenchyma. Leaf blade nodular in section, or adaxially flat. Midrib conspicuous; having a conventional arc of bundles; with colourless mesophyll adaxially (notably between the median bundle and its adaxial strand). Bulliforms present in discrete, regular adaxial groups; in simple fans (these large, occupying most of the epidermis). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming figures. Sclerenchyma all associated with vascular bundles.
Cytology. 2n = 40.
Classification. Watson & Dallwitz (1994): Panicoideae; Andropogonodae; Andropogoneae; Andropogoninae. Soreng et al. (2015): Panicoideae; Andropogonodae; Andropogoneae; Saccharinae. 2 species.
Distribution, phytogeography, ecology. Tropical Asia.
References, etc. Leaf anatomical: studied by us - P. irritans Hitchc.
Illustrations. • General aspect (P. contortum): E. Hickman. • P. irritans, abaxial epidermis of leaf blade: this project. • P. irritans, 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. delta-intkey.com/grass’.