The grass genera of the world
Habit, vegetative morphology. Perennial. Culms herbaceous. Leaf blades narrow; setaceous; rolled (involute); without cross venation.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality.
Inflorescence. Inflorescence a false spike, with spikelets on contracted axes (cylindrical, of short racemelets, basally enclosed in the upper leaf sheatrh); espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes very much reduced (to two contiguous spikelets); disarticulating (?); falling entire (the racemelets falling, cf. Tragus etc.?). Spikelets paired; not secund; consistently in long-and-short combinations. The shorter spikelets hermaphrodite. The longer spikelets hermaphrodite.
Female-fertile spikelets. Spikelets not noticeably compressed (?); falling with the glumes (with the racemelet?). Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes two; relatively large; exceeding the spikelets; long relative to the adjacent lemmas; hairless; not pointed; awnless; non-carinate; very dissimilar (indurated, tuberculate, acute, the lower ovate, the upper subglobose). Lower glume and the upper tuberculate. Upper glume distinctly saccate (enclosing the floret). Spikelets with female-fertile florets only.
Female-fertile florets 1. Lemmas less firm than the glumes (scarious); not becoming indurated; entire; blunt; awnless; hairless; non-carinate; without a germination flap. Palea present; conspicuous but relatively short (about half as long as the lemma); not indurated.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Microhairs present; chloridoid-type. Stomata common. Subsidiaries dome-shaped and triangular. Intercostal short-cells common (fairly); not paired (mainly solitary). Costal short-cells conspicuously in long rows. Costal silica bodies panicoid-type; dumb-bell shaped; not sharp-pointed.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+. Bulliforms present in discrete, regular adaxial groups; probably associated with colourless mesophyll cells to form deeply-penetrating fans (?). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the bundles); forming figures. Sclerenchyma all associated with vascular bundles.
Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae. 1 species (P. sessilis).
Distribution, phytogeography, ecology. Somalia.
Xerophytic; species of open habitats; halophytic. In coastal sand dunes.
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’.