Olmeca Soderstrom
Named for the Olmec Indians of Mexico.
Habit, vegetative morphology. Arborescent perennial; rhizomatous (the stems solitary, the rhizome necks up to 8 m long). The flowering culms leafy. Culms 150 cm high; woody and persistent; to 5 cm in diameter; branched above. Culm nodes glabrous. Primary branches/mid-culm node 1. Culm internodes solid, or hollow. Unicaespitose. Rhizomes pachymorph. Plants unarmed. Leaves not basally aggregated; non-auriculate; with auricular setae. Leaf blades broad; pseudopetiolate, or not pseudopetiolate; without cross venation; rolled in bud; truncate, or not truncate; 1–4 mm long. Contra-ligule present, or absent.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets. Not viviparous.
Inflorescence. Inflorescence determinate; paniculate; open; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes paniculate; with very slender rachides. ‘Articles’ glabrous. Spikelets pedicellate.
Female-fertile spikelets. Spikelets 30–40 mm long; not noticeably compressed; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairless; the rachilla extension with incomplete florets. Hairy callus absent.
Glumes two; very unequal; shorter than the adjacent lemmas; hairless; not pointed; awnless; non-carinate; similar. Lower glume longer than half length of lowest lemma. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped.
Female-fertile florets 3–12 (variable in number). Lemmas not becoming indurated; entire; pointed; awnless, or mucronate (?); hairless; non-carinate; without a germination flap; 7–11 nerved. Palea present; relatively long; apically notched; awnless, without apical setae; not indurated; 2-nerved, or several nerved (2–6); 2-keeled. Lodicules present; 3; free; membranous; ciliate; toothed, or not toothed; heavily vascularized. Stamens 3. Anthers not penicillate; without an apically prolonged connective. Ovary glabrous. Styles fused. Stigmas 2–3.
Fruit, embryo and seedling. Fruit large (1.5–2.5 cm in diameter); subglobose. Pericarp fleshy. Seed ‘non-endospermic’.
Seedling with a short mesocotyl. First seedling leaf without a lamina.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally (the costals rather smaller); of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; panicoid-type; 48–60 microns long; 6.9–9.6 microns wide at the septum. Microhair total length/width at septum 5.6–7.7. Microhair apical cells 24–33 microns long. Microhair apical cell/total length ratio 0.5–0.55. Stomata common; 25–30 microns long. Subsidiaries high dome-shaped (mostly), or triangular (some). Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs; silicified, or not silicified. Intercostal silica bodies when present, narrowly saddle shaped. Costal short-cells predominantly paired. Costal silica bodies saddle shaped (a narrowish version predominating), or oryzoid (some of the saddles being almost interpretable as such); not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with adaxial palisade; with arm cells; with fusoids. The fusoids external to the PBS. Leaf blade adaxially flat. Midrib conspicuous; having complex vascularization. The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups (a large group in each intercostal zone); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’ (the primaries and some of the smaller bundles with large ‘anchors’ or I’s). Sclerenchyma all associated with vascular bundles.
Taxonomy. Bambusoideae; Bambusodae; Bambuseae.
Distribution, ecology, phytogeography. 2 species; Mexico.
Holarctic and Neotropical. Madrean. Caribbean.
References, etc. Morphological/taxonomic: Sodertrom 1981e. Leaf anatomical: this project.
Special comments. Fruit data wanting.
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).