The grass genera of the world
Including Despretzia, Galeottia Mart. & Gal., Krombholzia Fourn., Senites Adans.
Habit, vegetative morphology. Perennial; stoloniferous, or decumbent. The flowering culms leafy. Culms 30–100 cm high; herbaceous; clambering or trailing; sparsely to amply branched above, or unbranched above. The branching simple. Plants unarmed. Leaves not basally aggregated; non-auriculate. Leaf blades lanceolate to ovate; broad, or narrow; pseudopetiolate (the pseudopetioles long and slender); cross veined; rolled in bud.
Reproductive organization. Plants bisexual, all with bisexual spikelets; without hermaphrodite florets (the lowermost florets in each spikelet female, the upper male). The spikelets all alike in sexuality.
Inflorescence. Inflorescence paniculate; open; with capillary branchlets; espatheate; not comprising partial inflorescences and foliar organs.
Female-fertile spikelets. Spikelets falling with the glumes; not disarticulating between the florets, or disarticulating between the florets (the upper, male part sometimes shed separately). Rachilla prolonged beyond the uppermost female-fertile floret; hairless; the rachilla extension with incomplete florets.
Glumes one per spikelet; shorter than the adjacent lemmas; not pointed (truncate to dentate, with cross nerves); awnless. Lower glume several-nerved. Upper glume 5 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets (male). The distal incomplete florets 1–14. Spikelets without proximal incomplete florets.
Female-fertile florets 1. Lemmas slightly gibbous; entire to incised; not deeply cleft (acute to truncate or dentate); awnless, or mucronate (?); hairless; 7–13 nerved. Palea present; awnless, without apical setae. Lodicules present; 2; free; fleshy. Stamens 0 (3 in the male florets). Stigmas 2.
Fruit, embryo and seedling. Hilum short. Embryo small; with an epiblast; with a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins overlapping.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (the costals narrower). Mid-intercostal long-cells rectangular; having markedly sinuous walls (deeply). Microhairs present; panicoid-type; 30–31–57 microns long; 3.6–5.7 microns wide at the septum. Microhair total length/width at septum 6.9–10. Microhair apical cells (12–)13–31.5(–33) microns long. Microhair apical cell/total length ratio 0.38–0.58. Stomata common; 21–33 microns long. Subsidiaries dome-shaped and triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare (but abundant microhairs and (small) microhair bases in Z. pittieri). Costal zones with short-cells. Costal short-cells conspicuously in long rows, or neither distinctly grouped into long rows nor predominantly paired (in Z. pittieri, the rows are interrupted by prickles). Costal silica bodies panicoid-type; cross shaped and nodular; not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; with adaxial palisade; without arm cells; without fusoids. Leaf blade adaxially flat. Midrib conspicuous (a larger bundle); with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans (the fans large, occupying about half the width of the mesophyll). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present. Sclerenchyma all associated with vascular bundles.
Cytology. 2n = 46.
Classification. Watson & Dallwitz (1994): Centothecoideae; Centotheceae. Soreng et al. (2015): Panicoideae; Zeugiteae. About 12 species.
Distribution, phytogeography, ecology. Mexico to Venezuela, West Indies.
Shade species; glycophytic. Ravines and bushy hillsides.
References, etc. Leaf anatomical: this project.
Illustrations. • Z. americanus: P. Beauv. (1812). • Z. americanus, as Despretzia mexicana: Kunth (1835). • Z. pringlei: U.S. Div. of Agrostology, via Wikimedia Commons
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’.