Actinocladum McClure ex Soderstrom
Name alluding to the manner of branching.
Habit, vegetative morphology. Perennial; caespitose. The flowering culms leafy. Culms 300–460 cm high; woody and persistent; to about 1.4 cm in diameter; branched above (and with rather different branches basally). Primary branches/mid-culm node 1 (apsidate). Culm sheaths persistent, or deciduous in their entirety. Culm internodes solid. Rhizomes pachymorph. Plants unarmed. Leaves not basally aggregated. Leaf blades broad; 10–40 mm wide; pseudopetiolate; disarticulating from the sheaths; rolled in bud; ligule present; a minute ciliolate rim.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality.
Inflorescence. Inflorescence consisting of verticils of racemose or paniculate, few-flowered ‘inflorescences’; spatheate; a complex of ‘partial inflorescences’ and intervening foliar organs (with a spatheole at the first node of each ultimate inflorescence unit). Spikelet-bearing axes ‘racemes’, or paniculate; clustered; persistent. Spikelets not secund; long pedicellate.
Female-fertile spikelets. Spikelets 60–75 mm long; slightly compressed laterally; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairy (short-pilose); the rachilla extension with incomplete florets. Hairy callus present (of short hairs).
Glumes two; very unequal; shorter than the adjacent lemmas; free; hairless; glabrous; pointed; awnless (apiculate); non-carinate (rounded on the back); similar (leathery, triangular). Lower glume relatively smooth; 5 nerved. Upper glume 11 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped. Spikelets without proximal incomplete florets.
Female-fertile florets 7–10. Lemmas ovate lanceolate; less firm than the glumes; not becoming indurated; entire; pointed; awnless; hairless; glabrous; non-carinate (rounded on the back); 13 nerved. Palea present; relatively long; minutely apically notched; awnless, without apical setae; not indurated; several nerved (6 between the keels, 5 on each wing); 2-keeled. Lodicules present; 3; free; membranous; ciliate, or glabrous; toothed; heavily vascularized. Stamens 3. Anthers not penicillate; without an apically prolonged connective. Ovary hairy; with a conspicuous apical appendage. The appendage broadly conical, fleshy. Styles fused (the top of the ovary being attenuate into a single style). Stigmas 2.
Fruit, embryo and seedling. Fruit large; not grooved (but the seed within it slightly grooved); slightly curved, compressed dorsiventrally; with hairs confined to a terminal tuft. Hilum long-linear. Pericarp dry, thick and hard; free. Embryo small.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; costal and intercostal. Intercostal papillae over-arching the stomata (and almost completely covering them); several per cell (basically one median row per long-cell, large, thick walled, irregular, warty and sometimes bifurcated or branching). Intercostal zones probably with typical long-cells (but their shapes largely obscured but papillae, and hard to determine). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; mostly clearly two-celled (but occasionally with an extra, short basal cell); panicoid-type; 40–48 microns long; 5.4–6 microns wide at the septum. Microhair total length/width at septum 7.5–8. Microhair apical cells 18–25.3 microns long. Microhair apical cell/total length ratio 0.44–0.53. Stomata common; 22.5–27 microns long. Guard-cells sunken. Intercostal short-cells absent or very rare. Numerous large costal prickles present, with abundant tiny pits and conspicuous basal rosettes. Crown cells absent. Costal short-cells predominantly paired. Costal silica bodies absent (in the material seen).
Transverse section of leaf blade, physiology. C3. Mesophyll with adaxial palisade; with arm cells; with fusoids. The fusoids external to the PBS. Leaf blade with distinct, prominent adaxial ribs (with one large rib and a short series of smaller ones, near one margin), or adaxially flat (elsewhere). Midrib not readily distinguishable (unless the submarginal rib represents a highly asymmetrical midrib); with one bundle only. The lamina symmetrical on either side of the midrib (unless the large submarginal rib is interpreted as a highly asymmetrically placed midrib). Bulliforms present in discrete, regular adaxial groups (between all the adjoining veins); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’ (all the bundles with narrow I’s or ‘anchors’). Sclerenchyma not all bundle-associated. The ‘extra’ sclerenchyma in abaxial groups and in adaxial groups; abaxial-hypodermal, the groups isolated and adaxial-hypodermal, contiguous with the bulliforms (there being small abaxial groups opposite the bulliforms, and adaxial hypodermal fibres adjoining and lateral to them).
Taxonomy. Bambusoideae; Bambusodae; Bambuseae.
Distribution, ecology, phytogeography. 1 species; central Brazil.
Neotropical. Central Brazilian.
References, etc. Morphological/taxonomic: Soderstrom 1981d. Leaf anatomical: this project.
Illustrations. • Abaxial epidermis of leaf blade. Actinocladum verticillatum.
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).
