The grass genera of the world
Habit, vegetative morphology. Robust perennial; rhizomatous to stoloniferous. Culms 20–120 cm high (? - resembling Ammophila in appearance); herbaceous; unbranched above. Culm nodes hidden by leaf sheaths. Leaves non-auriculate. Leaf blades broad (loosely inrolled); not pseudopetiolate. Ligule an unfringed membrane; up to 5–10 mm long.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate; open (diffuse); espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets not noticeably compressed; disarticulating above the glumes. Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes present; two; more or less equal; somewhat shorter than the spikelets to exceeding the spikelets; long relative to the adjacent lemmas (sometimes slightly shorter than them); awnless; non-carinate; similar. Lower glume 5–7 nerved. Upper glume 5–7 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.
Female-fertile florets 1. Lemmas not convolute; decidedly firmer than the glumes; not becoming indurated (chartaceous); entire to incised (square to slightly notched); not deeply cleft; awned. Awns 1; median; from a sinus to dorsal; non-geniculate; straight; deciduous. Lemmas densely hairy; non-carinate; 7–9 nerved. Palea present; relatively long (closely resembling the lemma); entire (acute); textured like the lemma; several nerved (5–9 nerved, hairy); keel-less. Lodicules present; 3; free; membranous; ciliate (near apex); not toothed; not or scarcely vascularized. Stamens 3. Anthers penicillate, or not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2; white.
Fruit, embryo and seedling. Fruit free from both lemma and palea; medium sized, or large (8–11 mm long); not noticeably compressed. Hilum long-linear. Pericarp free. Embryo small; not waisted. Endosperm hard; containing compound starch grains. Embryo with an epiblast; without a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins meeting.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Mid-intercostal long-cells having markedly sinuous walls. Microhairs absent. Stomata common; (31.5–)34.5–36(–39) microns long. Subsidiaries low to high dome-shaped, or triangular. Intercostal short-cells common; not paired (arranged like the costals); silicified. Intercostal silica bodies cubical. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies horizontally-elongated smooth, rounded, and tall-and-narrow (or cubical); not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma. Leaf blade with distinct, prominent adaxial ribs; with the ribs very irregular in sizes. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups (at the bases of the furrows); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the bundles); forming figures. Sclerenchyma not all bundle-associated. The extra sclerenchyma in abaxial groups (in the form of small abaxial strands midway between the bundles).
Classification. Watson & Dallwitz (1994): Stipoideae; Stipeae. Soreng et al. (2015): Pooideae; Stipeae. 1 species (P. villosa).
Distribution, phytogeography, ecology. Gobi Desert.
Xerophytic; species of open habitats. A robust, Ammophila-like sandbinder.
Rusts and smuts. Rusts Puccinia.
References, etc. Morphological/taxonomic: Bor 1951; Macfarlane and Watson 1980. Leaf anatomical: Metcalfe 1960, and studied by us.
Illustrations. • P. villosa, as Arundo: Trinius, Species Graminum III (1836)
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’.