Chasmanthium Link
Excluding Gouldochloa
Habit, vegetative morphology. Erect perennial; rhizomatous, or caespitose. Culms 50–150 cm high; herbaceous; unbranched above. Culm nodes glabrous. Culm internodes hollow. Young shoots extravaginal. Leaves not basally aggregated; non-auriculate; without auricular setae. Leaf blades linear to lanceolate; broad; 10–20 mm wide (and 7 to 20 cm long); flat, or folded; not pseudopetiolate; without cross venation; persistent; rolled in bud; a fringed membrane; truncate. Contra-ligule absent.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets; exposed-cleistogamous, or chasmogamous.
Inflorescence. Inflorescence few spikeleted to many spikeleted; paniculate, or of spicate main branches (the primary branches reduced to racemes); open, or contracted; non-digitate; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets morphologically ‘conventional’, or unconventional (in having supernumerary proximal sterile lemmas); 5–35 mm long; cuneate; markedly compressed laterally; disarticulating above the glumes (or above the sterile lemmas); disarticulating between the florets; with conventional internode spacings. Rachilla prolonged beyond the uppermost female-fertile floret. Hairy callus present, or absent. Callus absent, or short.
Glumes two; very unequal to more or less equal; shorter than the spikelets; shorter than the adjacent lemmas; hairless (apart from the keel); pointed (acute, acuminate, or rarely mucronate); awnless; carinate; similar (rigid, compressed). Lower glume 3–7 nerved. Upper glume 3–7 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets, or both distal and proximal to the female-fertile florets. The distal incomplete florets merely underdeveloped. Spikelets with proximal incomplete florets. The proximal incomplete florets 1–6; paleate, or epaleate; sterile. The proximal lemmas awnless; 5–11 nerved (?); exceeded by the female-fertile lemmas; similar in texture to the female-fertile lemmas; not becoming indurated.
Female-fertile florets 2–12 (or occasionally reduced to one, in few-spikeleted inflorescences). Lemmas acute to acuminate; less firm than the glumes to similar in texture to the glumes (papery); not becoming indurated; entire; pointed; awnless; hairless; glabrous; carinate (sometimes markedly flattened); without a germination flap; 7–11 nerved. Palea present (rigid, bowed at the base); relatively long; entire; awnless, without apical setae; textured like the lemma; 2-nerved; 2-keeled. Palea keels narrowly winged, or wingless. Lodicules present; 2; free; fleshy; glabrous; not or scarcely vascularized. Stamens 1(–3); with free filaments. Ovary glabrous. Styles free to their bases. Stigmas 2; red pigmented.
Fruit, embryo and seedling. Fruit free from both lemma and palea (loosely enclosed); dark brown to black; compressed laterally. Hilum short. Embryo large. Endosperm hard; without lipid; containing only simple starch grains. Embryo with an epiblast; with a scutellar tail; with an elongated mesocotyl internode. Embryonic leaf margins overlapping.
First seedling leaf with a well-developed lamina. The lamina 7 veined.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Mid-intercostal long-cells rectangular, or rectangular and fusiform; having markedly sinuous walls, or having markedly sinuous walls and having straight or only gently undulating walls (in C. laxum). Microhairs present; panicoid-type; 42–54 microns long; 4.5–6 microns wide at the septum. Microhair total length/width at septum 7–11.3. Microhair apical cells 21–24(–33) microns long (C. latifolium), or 15–18 microns long (C. laxum). Microhair apical cell/total length ratio 0.31–0.33 (C. laxum), or 0.47–0.61 (C. latifolium). Stomata common; 15–21 microns long. Subsidiaries dome-shaped, or dome-shaped and triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common (fairly), or absent or very rare; not paired (solitary); not silicified. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with adaxial palisade, or without adaxial palisade (this not apparent in the two species seen); without arm cells; without fusoids. Leaf blade with distinct, prominent adaxial ribs to adaxially flat. Midrib conspicuous (conspicuously keeled or not); with one bundle only (larger than the rest), or having a conventional arc of bundles (the large median accompanied by small laterals); with colourless mesophyll adaxially (e.g. C. laxum), or without colourless mesophyll adaxially (e.g. C. latifolium). Bulliforms present in discrete, regular adaxial groups; in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the bundles); forming ‘figures’ (all the bundles with conspicuous ‘anchors’). Sclerenchyma all associated with vascular bundles.
Culm anatomy. Culm internode bundles in one or two rings, or scattered.
Cytology. Chromosome base number, x = 12. 2n = 24. 2 ploid. Nucleoli persistent.
Taxonomy. Centothecoideae; Centotheceae.
Distribution, ecology, phytogeography. 6 species; southeastern U.S.A. and northern Mexico. Shade species; glycophytic. Moist woodland to semiarid scrub.
Holarctic. Boreal and Madrean. Atlantic North American. Canadian-Appalachian, Southern Atlantic North American, and Central Grasslands.
References, etc. Morphological/taxonomic: Yates 1966b. Leaf anatomical: this project.
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).