Gardens' Bulletin Singapore 69(2): 179-187. 2017 
doi: 10.26492/gbs69(2).2017-03 
179 
Novitates Bruneienses, 9. A synopsis of Epirixanthes 
(Polygalaceae) in Brunei Darussalam 
and notes on species elsewhere 
M. Dancak 1 , M. Hrones 2 , R.S. Sukri 3 , F. Metali 3 & A.A. Joffre 4 
department of Ecology & Environmental Sciences, Faculty of Science, Palacky University 
Slechtitelu 27, CZ-78371 Olomouc, Czech Republic 
martin. dancak@upol. cz 
department of Botany, Faculty of Science, Palacky University 
Slechtitelu 27, CZ-78371 Olomouc, Czech Republic 
Environmental and Life Sciences Programme, Faculty of Science, Universiti Brunei 
Darussalam, Jalan Tungku Link, BE 1410, Brunei Darussalam 
4 Brunei National Herbarium, Forestry Department, Ministry of Primary Resources and 
Tourism, Jalan Menteri Besar, Berakas, BB3910 Brunei Darussalam 
ABSTRACT. The genus Epirixanthes Blume is revised for Brunei Darussalam. Four 
species are recognised for the country: Epirixanthes cylindrica Blume, E. elongata Blume, 
E. kinabaluensis T.Wendt and E. papuana J.J.Sm., with the two latter species being newly 
recorded for the Brunei flora. A single collection from Brunei that was formerly identified as 
Epirixanthes pallida T.Wendt is now confirmed as E. papuana. A revised key for the genus is 
included. 
Keywords. Distribution, herbs, Malesia, mycoheterotrophic plants, north-western Borneo, 
taxonomy, understorey 
Introduction 
Epirixanthes Blume is a species-poor genus of holomycoheterotrophic herbaceous 
plants from the family Polygalaceae which inhabit the understorey of tropical 
rainforests (Van der Meijden, 1988; Merckx et al., 2013). It is sister to the autotrophic 
genus Salomonia Lour, with which it shares several synapomorphies such as spilce-like 
terminal inflorescence and three antesepalous stamen primordia (Van der Meijden, 
1988; Mennes et al., 2015). Members of the genus are generally tiny plants with 
reduced bract-like leaves and dense spike-like inflorescences (Van der Meijden, 1988). 
Due to the reduction of vegetative organs as a result of mycoheterotrophy, the set of 
morphological characters useful for species determination is very limited and includes 
mostly reproductive organs (i.e., bracts, bracteoles, sepals and fruits). Currently, only 
seven species of Epirixanthes are recognised worldwide, and all of them are endemic 
to Indo-Malesia (Van der Meijden, 1988; Pendry, 2010; Tsukaya et al., 2016). The 
centre of its taxonomic diversity lies in Borneo where six of the species co-occur, with 
one of them apparently endemic to the island (Fig. 1). In the Checklist of the Flowering 
