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THAI FOR. BULL. (BOT.) 36: 52–60. 2008.

The tribe Centotheceae (Poaceae) in Thailand

MONTHON NORSAENGSRI* & PRANOM CHANTARANOTHAI*

ABSTRACT. Two genera and three species are recognized for the tribe Centotheceae in Thailand. Keys to the genera and species, together with descriptions and illustrations, are provided.

Tribe Centotheceae consists of 11 genera and 33 species, all exhibiting a tropical distribution. The tribe was established by Ridley (1907) in subfamily Pooideae of the Poaceae. The tribe consists of two genera, Centotheca and Lophatherum, which are restricted to Southeast Asia. Ridley’s work has been accepted by many botanists such as Bor (1960), Gilliland et al. (1971) and Koyama (1987). Clayton & Renvoize (1986) placed the tribe in subfamily Centothecoideae and considered it to be most close to Chloridoideae. Watson & Dallwitz (1992) placed the tribe under the supertribe Orysoidae in Bambusoideae. Common characters are cross-nerves in the leaves and pseudopetioles; 1-many flowered spikelets that are bisexual with the upper florets reduced, laterally compressed and disarticulating below the glumes; glumes subequal or unequal, chartaceous, shorter than the spikelet; fertile lemma usually 5–9-nerved, chartaceous, glabrous with bulbose-based bristles near the margins, awnless or with a retrosely scabrid awn from the tip; palea hyaline, 2-keeled; lodicules 2, cuneate; stamens 2 or 3; and stigmas 2, shortly connate at base.

Two genera and three species are recognized in Thailand.

KEY TO THE GENERA

1. Florets 1–3, bisexual, upper lemmas awnless with sub-marginal bulbous-based bristles

Centotheca

1. Florets more than 3, only the lowest bisexual, the upper reduced and sterile; all lemmas awned and

forming a brush-like tuft of awns from apex of spikelet, bristles absent

Lophatherum

CENTOTHECA

Desv. in Nouv. Bull. Sci. Soc. Philom. Paris 2: 189. 1810, as ‘Centosteca’orth. cons.

Perennials; culms erect. Leaf blades broadly elliptic to lanceolate. Ligule membranous. Inflorescence an open panicle. Spikelets laterally compressed, with 1–3 florets. Glumes membranous or chartaceous. Lemmas chartaceous, 5–7-nerved, awnless, with sub-marginal retrorse tubercle-based bristles. Paleas boat-shaped, 2-keeled.

  • *

    Applied Taxonomic Research Center, Department of Biology, Faculty of Science, Khon Kaen University,

Khon Kaen 40002, Thailand.

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