Schizostachyum, Nees, 1829

Merklinger, Felix F., Chhang, Phourin & Abstract, K. M. Wong, 2017, Schizostachyum cambodianum, a new species of bamboo (Poaceae: Bambusoideae) from Cambodia, Phytotaxa 298 (1), pp. 83-88 : 83-84

Schizostachyum bamboos

The genus Schizostachyum Nees (1829: 535) belongs to the Melocanninae subtribe of the Bambuseae. Other genera in this subtribe include Melocanna Trinius (1821: 43) , Cephalostachyum Munro (1868: 138) , Ochlandra Thwaites (1864: 376) , Pseudostachyum Munro (1868: 141) , Teinostachyum Munro (1868: 142) , Neohouzeaua A. Camus (1922: 100) , Dendrochloa C.E. Parkinson (1933: 707) and Leptocanna L.C.Chia & H.L.Fung (1981: 212; e.g. BPG, 2012; Kellogg, 2015). All these genera have several characters in common, including a conspicuous white waxy band below each node ( Wong, 1995), a typical expression of the mid-culm branch complement as many subequal higher-order branches developing from a single primary branch bud, and a glabrous ovary attenuating into a rigid hollow apical extension or style containing a central tissue strand ( Holttum, 1956).

Varying views regarding the definition of genera in the Melocanninae subtribe have been expressed. Holttum (1946) suggested that connateness of filaments does not seem to be a strong enough character for generic delineation and subsequently ( Holttum 1954, 1956) included Neohouzeaua into his concept of Schizostachyum . A similar view was taken by Xia (1993), who recognised Cephalostachyum and Pseudostachyum as distinct genera, but included Dendrochloa , Leptocanna , Neohouzeaua and Teinostachyum within Schizostachyum .

Neohouzeaua was first described by A. Camus (1922) (type: N. mekongensis A. Camus 1922: 101 ) based on flowering material only. It was set apart from Schizostachyum by its lack of a rachilla extension beyond the fertile floret, absence of lodicules, and the filaments connate into a tube. However, species later added into Neohouzeaua do have a rachilla extension, such as in N. dulloa ( Gamble 1896: 101) A. Camus (1922: 101) or N. helferi ( Munro 1868: 114) Gamble (1923: 91) , and N. tavoyana Gamble (1923: 92) sometimes has lodicules.

Neohouzeaua occurs in our study area and has some vegetative affinities with the new Schizostachyum species, such as a lanceolate and reflexed culm sheath blade and a truncate apex of the culm sheath ( Dransfield, 1998). However, the species described here has free filaments, which sets it apart from the concept of Neouhouzeaua, based on the type N. mekongensis . Also, no large basal projections have been mentioned in descriptions of the culm sheaths of Neohouzeaua . Other comparison is hampered by the uncertainty of vegetative features of Neohouzeaua due to the lack of herbarium specimens.

While it may seem too early still to assess the taxonomic importance of characters for separating Neohouzeaua from Schizostachyum , our new species is consistent with the type of Schizostachyum , S. blumei Nees (1829: 535) , in having pseudospikelets that end in a pronounced rachilla extension and terminal vestigial flower, absence of glumes and lodicules, and presence of three stigmas. It differs from the type and several other species in the genus in having a glabrous lemma and palea (the type species has a pubescent lemma and palea surface).