Symplectrodia Lazarides
From the Greek sym- (together or united), plekton (a spur) and odous (tooth), contrasting an entire basal lemma with 3-toothed or 3-lobed lemmas in the related genus Triodia.
Habit, vegetative morphology. Perennial (robust or slender); caespitose (and rhizomatous). Culms 30–135 cm high. Culm nodes hairy, or glabrous. Culm internodes solid. The shoots not aromatic. Leaves not basally aggregated; non-auriculate; with hair tufts in the ligule region. Sheath margins free. The basal sheaths sometimes reddish brown or with woolly hairs. Leaf blades narrow; acicular; hard, woody, needle-like (cf. Triodia); without abaxial multicellular glands; without cross venation; a fringe of hairs. Contra-ligule absent.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate; open to contracted. Inflorescence with axes ending in spikelets. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; not secund; long pedicellate.
Female-fertile spikelets. Spikelets not noticeably compressed; disarticulating above the glumes; disarticulating between the florets; with distinctly elongated rachilla internodes between the florets (the internode above the fertile floret up to 5 mm long and adnate to the palea, and the upper internodes also elongated at maturity, with the sterile florets ultimately disarticulating individually). Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Hairy callus present. Callus pointed (curved or oblique).
Glumes two; very unequal; shorter than the spikelets to about equalling the spikelets; long relative to the adjacent lemmas; hairless; usually glabrous; pointed; awned to awnless (often aristulate); non-carinate (rounded or flattened dorsally); similar (cartilaginous, lanceolate-elliptic, acuminate). Lower glume 1–5 nerved. Upper glume 3–7 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets (without paleas, often reduced). The distal incomplete florets 2–5; clearly specialised and modified in form (empty, cartilaginous, 3-lobed, 3-nerved, unequally 3-awned, finally becoming distant and prominently exserted by elongation of the internodes); awned. Spikelets without proximal incomplete florets.
Female-fertile florets 1. Lemmas similar in texture to the glumes (cartilaginous); entire; pointed; awned. Awns 1; median; apical; non-geniculate; hairless; much shorter than the body of the lemma to about as long as the body of the lemma. Lemmas hairy (marginally and on the midnerve), or hairless; without a germination flap; 3 nerved. Palea present; relatively long; entire (acute); awnless, without apical setae; hardened and adnate to the rachilla below; 2-nerved; 2-keeled. Lodicules present; 2; fleshy; glabrous; not or scarcely vascularized. Stamens 3. Anthers not penicillate; without an apically prolonged connective. Ovary glabrous; without a conspicuous apical appendage. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit small to medium sized (4–4.5 mm long); ellipsoid; longitudinally grooved (on the hilar face); compressed dorsiventrally. Hilum short. Pericarp fused. Embryo large.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous (the intercostal zones sunken in narrow grooves, inaccessible for observation in surface view). Papillae present; intercostal, or costal and intercostal. Intercostal papillae not over-arching the stomata; consisting of one oblique swelling per cell, or consisting of one symmetrical projection per cell, or several per cell. Microhairs present; elongated; clearly two-celled; chloridoid-type. Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhairs about 39 microns long (where recordable); 15 microns wide at the septum. Microhair total length/width at septum 2.6. Microhair apical cells 7.5 microns long. Microhair apical cell/total length ratio 0.19. Stomata not observable; 18–21 microns long. Subsidiaries papillate, or non-papillate. Costal short-cells conspicuously in long rows. Costal silica bodies present in alternate cell files of the costal zones; ‘panicoid-type’; dumb-bell shaped (large and sometimes very asymmetric); not sharp-pointed.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section infolded permanently; circular. The adaxial channel parallel-sided, with a digitate base.
C4. The anatomical organization unconventional. Organization of PCR tissue Triodia type (PCR ‘sheaths’ lateral only or ‘draping’). XyMS+. PCR sheath outlines even, or uneven to even. Mesophyll traversed by columns of colourless mesophyll cells (linking the adaxial and abaxial grooves); with arm cells (cf. Sclerodactylon, Triodia). Leaf blade ‘nodular’ in section; with the ribs very irregular in sizes. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups; associated with colourless mesophyll cells to form deeply-penetrating fans (incorporated in or linked with the colourless girders). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’ (large anchors). Sclerenchyma not all bundle-associated. The ‘extra’ sclerenchyma in a continuous abaxial layer.
Taxonomy. Chloridoideae; Triodieae.
Distribution, ecology, phytogeography. 2 species; Australia. Xerophytic; species of open habitats.
Australian. North and East Australian. Tropical North and East Australian.
References, etc. Morphological/taxonomic: Lazarides 1985. Leaf anatomical: this project.
Illustrations. • Spikelet (glumes removed). • Callus. • Abaxial epidermis of leaf blade. • Transverse section 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).
