Ixophorus Schlechtd.
Habit, vegetative morphology. Annual, or perennial; caespitose. Culms herbaceous; unbranched above. Culm nodes glabrous. Culm internodes solid. Leaves not basally aggregated; non-auriculate. Leaf blades broad; without cross venation; persistent; a fringed membrane; truncate; 1.5 mm long.
Reproductive organization. Plants bisexual, with bisexual spikelets; without hermaphrodite florets (the second floret being female-only).
Inflorescence. Inflorescence of spicate main branches; open. Inflorescence axes not ending in spikelets. Rachides hollowed. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets subtended by solitary ‘bristles’ (each subtended and exceeded by a single, sticky bristle). The ‘bristles’ persisting on the axis. Spikelets solitary; secund (the branches dorsiventral).
Female-fertile spikelets. Spikelets 3.5 mm long; abaxial; compressed dorsiventrally; falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes two; very unequal; (the longer) long relative to the adjacent lemmas (almost equalling the spikelet, the lower much shorter); dorsiventral to the rachis; hairless; glabrous; pointed; awnless; non-carinate; similar (herbaceous). Lower glume 3 nerved. Upper glume 11 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets (the latter being female-only). 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 (hyaline at first, then developing expanded leathery flanks and winged keels clasping the upper floret). The proximal incomplete florets male. The proximal lemmas awnless; 5 nerved; decidedly exceeding the female-fertile lemmas; less firm than the female-fertile lemmas (cartilaginous); not becoming indurated.
Female-fertile florets 1. Lemmas decidedly firmer than the glumes; minutely striate; not becoming indurated (tough); mucronate; hairless; non-carinate; having the margins inrolled against the palea; with a clear germination flap; 5 nerved. Palea present (firm, rugulose between the veins); relatively long; tightly clasped by the lemma (enclosed by it at its tip); 2-nerved; 2-keeled. Lodicules present; 2; free; fleshy; glabrous; not or scarcely vascularized. Stamens 0. Ovary glabrous. Styles basally fused. Stigmas 2; red pigmented.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small (about 3 mm long); compressed dorsiventrally. Hilum short. Embryo large; waisted. Endosperm hard.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally; of similar wall thickness costally and intercostally. Intercostal zones exhibiting many atypical long-cells (many being quite short). Mid-intercostal long-cells intercostal long-cells variable - some rectangular, some fusiform, many short; having markedly sinuous walls. Microhairs present; panicoid-type; 49–51 microns long; 8.4–9 microns wide at the septum. Microhair total length/width at septum 5.7–6.1. Microhair apical cells 31.5–36 microns long. Microhair apical cell/total length ratio 0.62–0.71. Stomata common; 37.5–48 microns long. Subsidiaries mostly dome-shaped. Guard-cells overlapped by the interstomatals, or overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’; short butterfly shaped and dumb-bell shaped, or cross shaped.
Transverse section of leaf blade, physiology. C4; XyMS– (median midrib bundle XyMS+, the rest XyMS-). Leaf blade ‘nodular’ in section; with the ribs more or less constant in size. Midrib conspicuous; having a conventional arc of bundles; with colourless mesophyll adaxially. Bulliforms present in discrete, regular adaxial groups (in places, but the epidermis mostly irregularly bulliform); occasionally in simple fans. Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present.
Taxonomy. Panicoideae; Panicodae; Paniceae.
Distribution, ecology, phytogeography. 2–3 species; Mexico. Species of open habitats. Weedy places.
Neotropical. Caribbean.
Rusts and smuts. Rusts — Puccinia. Taxonomically wide-ranging species: Puccinia chaetochloae.
References, etc. Leaf anatomical: this project.
Illustrations. • Germination flap. Ixophorus unisetus. Plateau-like flap. • Abaxial epidermis of leaf blade
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).
