Steinchisma Raf.
Sometimes referred to Panicum (Subgenus Steinchisma, including (e.g.) Panicum hians = P. milioides
Habit, vegetative morphology. Perennial. Culms herbaceous. Leaf blades not pseudopetiolate; without cross venation.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality.
Inflorescence. Inflorescence paniculate; more or less contracted; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate. Pedicel apices cupuliform. Spikelets not in distinct ‘long-and-short’ combinations.
Female-fertile spikelets. Spikelets compressed dorsiventrally; falling with the glumes; with conventional internode spacings. The upper floret not stipitate. Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes two; very unequal (the lower short); (the upper) long relative to the adjacent lemmas (almost as long as the spikelet); without conspicuous tufts or rows of hairs; awnless; non-carinate. Lower glume shorter than the lowest lemma. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; paleate. Palea of the proximal incomplete florets fully developed; becoming conspicuously hardened and enlarged laterally. The proximal lemmas awnless; 3 nerved; less firm than the female-fertile lemmas.
Female-fertile florets 1. Lemmas not saccate; decidedly firmer than the glumes; smooth; becoming indurated; entire; awnless; non-carinate; having the margins inrolled against the palea; with a clear germination flap. Palea present; awnless, without apical setae. Ovary glabrous. Stigmas 2.
Fruit, embryo and seedling. Hilum short. Embryo large.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells differing markedly in wall thickness costally and intercostally (the costals thinner walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; panicoid-type; of S. hians 54–57 microns long; 5.4–6 microns wide at the septum. Microhair total length/width at septum 9–10. Microhair apical cells 27–34.5 microns long. Microhair apical cell/total length ratio 0.5–0.65. Stomata common; in S. hians 21–24 microns long. Subsidiaries mostly high dome-shaped, or triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs and not paired (mostly ostensibly solitary, but a few obvious pairs); not silicified (in the material of S. hians seen). Small intercostal prickles abundant. Crown cells absent. Costal short-cells conspicuously in long rows. Costal silica bodies abundant, ‘panicoid-type’; cross shaped, butterfly shaped, and dumb-bell shaped (short); not sharp-pointed.
Transverse section of leaf blade, physiology. C3 to C4 (intermediate in all three species tested, with C3-like mesophyll layout). The anatomical organization unconventional (in that there are some organelles in the outer sheath). XyMS+. PCR cell chloroplasts centripetal. Mesophyll with non-radiate chlorenchyma; without adaxial palisade. Leaf blade with distinct, prominent adaxial ribs to ‘nodular’ in section; with the ribs more or less constant in size (round topped). Midrib not readily distinguishable; with one bundle only. The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups (in all the furrows); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’ (all the bundles with I’s or ‘anchors’). Sclerenchyma all associated with vascular bundles.
Phytochemistry. Leaves containing flavonoid sulphates, or without flavonoid sulphates.
Taxonomy. Panicoideae; Panicodae; Paniceae.
Distribution, ecology, phytogeography. 4 species; Southern U.S.A. to Argentina. Commonly adventive. Mesophytic. Damp grassland.
Holarctic and Neotropical. Boreal and Madrean. Caribbean, Venezuela and Surinam, Amazon, Central Brazilian, and Pampas.
Economic importance. Significant weed species: S. hians.
References, etc. Leaf anatomical: this project.
Illustrations. • Transverse section of leaf blade. Steinchisma hians.
Cite this publication as: Watson, L., and Dallwitz, M. J. (1992 onwards). ‘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.’ http://biodiversity.uno.edu/delta/. Version: 18th August 1999. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993 onwards, 1998), and Watson and Dallwitz (1994), and Watson, Dallwitz, and Johnston (1986) should also be cited (see References).
