The grass genera of the world
Including Graya Steud., Steudelella Honda
Habit, vegetative morphology. Annual; stoloniferous and decumbent. Culms 5–15 cm high; herbaceous. Culm nodes hairy. Culm internodes hollow. Leaves not basally aggregated; non-auriculate. Leaf blades ovate; broad, or narrow; 3–10 mm wide (small but relatively broad, Commelina-like); cordate (amplexicaul); not pseudopetiolate; obscurely cross veined; persistent. Ligule a fringe of hairs.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate; open; with capillary branchlets; espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets seemingly morphologically conventional; 0.8–1.4 mm long; not noticeably compressed; falling with the glumes (but the glumes often deciduous). Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes present; assumed to be two (since the inflorescence is not contracted); relatively large; more or less equal; shorter than the adjacent lemmas; not pointed (obtuse); awnless; similar (cymbiform, hyaline). Lower glume 0 nerved. Upper glume 1 nerved. Spikelets with female-fertile florets only (i.e., a necessary corollary, assuming there are 2 glumes); without proximal incomplete florets.
Female-fertile florets 1. Lemmas similar in texture to the glumes (hyaline); not becoming indurated; entire; pointed to blunt; hairy; non-carinate (cymbiform); having the margins lying flat on the palea; without a germination flap; 1 nerved, or 2 nerved. Palea present; entire (oblong,obtuse); awnless, without apical setae; textured like the lemma; not indurated; 2-nerved. Lodicules present (minute); 2. Stamens 3. Anthers not penicillate. Ovary apically glabrous. Styles fused. Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small (about 0.5 mm long). Hilum short.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present (many intercostal cells papillate). Intercostal papillae over-arching the stomata; consisting of one oblique swelling per cell to consisting of one symmetrical projection per cell. Intercostal zones without typical long-cells (cf. Isachne). Mid-intercostal long-cells having straight or only gently undulating walls. Microhairs present; chloridoid-type (the apical cell somewhat pointed, but thick-walled and broader than long); 16.5 microns long; 7.5 microns wide at the septum. Microhair total length/width at septum 2.2. Microhair apical cells 9 microns long. Microhair apical cell/total length ratio 0.55. Stomata common. Subsidiaries parallel-sided to triangular (rather irregular forms, owing to bulbously-intruding surrounding cells); including both triangular and parallel-sided forms on the same leaf. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare (simply not detectable in this kind of epidermis). Costal short-cells conspicuously in long rows. Costal silica bodies panicoid-type to acutely-angled; acutely angled cross shaped; sharp-pointed (acutely angled crosses).
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with radiate chlorenchyma; Isachne-type. Leaf blade with distinct, prominent adaxial ribs; with the ribs more or less constant in size. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups (in the shallow furrows); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming figures. Sclerenchyma all associated with vascular bundles.
Cytology. Chromosome base number, x = 10. 2n = 20.
Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Isachneae. Soreng et al. (2015): Micrairoideae; Isachneae. 1 species (S. malaccense).
Distribution, phytogeography, ecology. India to southern China, Formosa, Malay Peninsula, Banka.
Helophytic to mesophytic.
References, etc. Leaf anatomical: Metcalfe 1960; studied by us.
Illustrations. • S. malaccense: Wu Zhengyi, Flora Yunnanica 9 (2003)
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’.