Grass Genera of the World

L. Watson and M. J. Dallwitz


Plagiantha Renvoize

Habit, vegetative morphology. Annual (or short-lived); loosely caespitose. Culms 30–80 cm high; herbaceous. Leaves not basally aggregated. Leaf blades lanceolate; narrow; 3–7 mm wide; without cross venation; persistent.

Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality.

Inflorescence. Inflorescence paniculate; open; with capillary branchlets; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate. Pedicel apices oblique. Spikelets not in distinct ‘long-and-short’ combinations.

Female-fertile spikelets. Spikelets 2.2–2.8 mm long; compressed dorsiventrally; falling with the glumes. The upper floret not stipitate. Rachilla terminated by a female-fertile floret.

Glumes two; very unequal; (the upper) about equalling the spikelets; (the upper) long relative to the adjacent lemmas; hairless; not pointed; awnless; non-carinate. Lower glume about 0.25 times the length of the upper glume; 3–5 nerved. Upper glume 5 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. 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. The proximal lemmas two-keeled, sulcate and nerveless between them; awnless; 4 nerved; slightly exceeded by the female-fertile lemmas; less firm than the female-fertile lemmas (membranous); not becoming indurated.

Female-fertile florets 1. Lemmas papillose; not becoming indurated; pallid; entire (and apiculate); awnless; hairless; non-carinate; having the margins inrolled against the palea. Palea present; relatively long; tightly clasped by the lemma; awnless, without apical setae; textured like the lemma.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (the costals much narrower); of similar wall thickness costally and intercostally (thin walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; panicoid-type. Stomata common. Subsidiaries low dome-shaped. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; not paired (solitary, rectangular, often large); not silicified. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’; butterfly shaped to nodular (ranging from short to elongated); not sharp-pointed.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll somewhat noticeably, in places, with radiate chlorenchyma; without adaxial palisade; Isachne-type to not Isachne-type. Leaf blade ‘nodular’ in section to adaxially flat. Midrib conspicuous; with one bundle only, or having a conventional arc of bundles (a large median, with a small bundle on either side which could be considered part of the midrib); with colourless mesophyll adaxially. The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups (these wide, one in each of the slight furrows); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (primaries only); forming ‘figures’ (the midrib median and some other primaries with anchors). Sclerenchyma all associated with vascular bundles.

Taxonomy. Panicoideae; Panicodae; Paniceae.

Distribution, ecology, phytogeography. 1 species; Brazil. Mesophytic; shade species; glycophytic.

Neotropical. Central Brazilian.

References, etc. Morphological/taxonomic: Renvoize 1982. Kew Bull. 37, 323. 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).

Index