The grass genera of the world
Habit, vegetative morphology. Rambling annual; decumbent (?). Culms 100–200 cm high; herbaceous; branched above. Culm nodes hairy. Leaves not basally aggregated. Leaf blades lanceolate; broad; 15–20 mm wide; cordate to sagittate; pseudopetiolate (with long petioles); without cross venation. Ligule a fringed membrane.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant, or all alike in sexuality; hermaphrodite and sterile (sterile at the tip of main inflorescence axis).
Inflorescence. Inflorescence a false spike, with spikelets on contracted axes (the lateral branches comprising spikelets and bristles organized in cuneate, peduncled burrs, the burrs racemosely and loosely borne on a slender, wavy rachis); a raceme of burrs, by contrast with the sessile burrs of Cenchrus. Inflorescence axes not ending in spikelets (the main rachis and the burr-like branches terminating in spiny bristles). Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes very much reduced (to pedunculate burrs of spikelets-plus-bristles); disarticulating; falling entire (the burrs falling entire with their peduncles). Spikelets with involucres of bristles (the spinescent bristles dichotomising from two basal stumps, forming a basketlike support for the spikelets). The bristles spiny, markedly coalescent basally; deciduous with the spikelets. Spikelets solitary; not secund.
Female-fertile spikelets. Spikelets 3.5 mm long; compressed dorsiventrally; falling with the glumes (in the burr). Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes two; very unequal to more or less equal; shorter than the adjacent lemmas; hairless; awnless. Lower glume 0 nerved. Upper glume 3 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. The proximal incomplete florets 1; epaleate; sterile. The proximal lemmas awnless.
Female-fertile florets 1. Lemmas decidedly firmer than the glumes; striate (minutely verrucose); becoming leathery; awnless, or mucronate (?); hairless; non-carinate; 5 nerved. Palea present; 2-nerved. Lodicules present; 2; free. Stamens 3. Anthers not penicillate. Ovary apically glabrous. Styles fused. Stigmas 2.
Fruit, embryo and seedling. Fruit small (2 mm long); compressed dorsiventrally. Hilum short. Embryo large.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; panicoid-type; (54–)60–78 microns long; (5.4–)5.7–6(–7.2) microns wide at the septum. Microhair total length/width at septum 8.3–14.4. Microhair apical cells (34–)37.5–49.5(–54) microns long. Microhair apical cell/total length ratio 0.63–0.69. Stomata common; 22.5–27 microns long. Subsidiaries dome-shaped (mostly), or triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare. Costal short-cells conspicuously in long rows (the rows interrupted by large prickles). Costal silica bodies panicoid-type; mostly cross shaped and dumb-bell shaped (short); not sharp-pointed.
Transverse section of leaf blade, physiology. C4; XyMS. Midrib conspicuous (via its keel); with one bundle only. Bulliforms not present in discrete, regular adaxial groups (epidermis seemingly extensively bulliform). Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present (primaries only - most larger bundles with abaxial girders only, or with abaxial girders and adaxial strands); nowhere forming figures. Sclerenchyma all associated with vascular bundles.
Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae. Soreng et al. (2015): Panicoideae; Panicodae; Paniceae; Cenchrinae. 1 species (S. sagittifolius).
Distribution, phytogeography, ecology. Angola.
References, etc. Morphological/taxonomic: Hughes 1923. Leaf anatomical: studied by us.
Illustrations. • S. sagittifolius: D.K. Hughes, Kew Bull. 1923. • S. sagittifolius, 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’.