Cheilotheca malayana Scortechini ex J. D. Hooker
Firstly described by Scortechini in Hooker (1887), accepted by Wallace (1975) and Stevens et al. (2004). C. malayana, is known from three collections by Scortechini, Kunstler and Ridley (the last one got lost, Sleumer 1967, p. 669-670), close together in Perak State, West Malaysia, south of Thailand. Wallace (1975) accepts only one characteristic to distinguish between the two sister species: C. khasiana has elongate, separate, longitudinally dehiscent thecae, the slit is lateral. In the original description of C. malayana (Scortechini in Hooker 1887), the thecae are depicted as short, horseshoe-like and apically connected. Father B. Scortechini has sent alkohol material as well as an annotated drawing of that species to Hooker, from which the description is prepared. Scortechini died as 'a victim of the climate' (Hooker 1887) before its publication.
Cheilos (gr.) = lip, margin.
There is a short description of another Cheilotheca species in Keng (1974), Cheilotheca sleumeriana. POWO accepts this description as well as WFO (spelling it C. sleumerana), probably because it might fullfill the formal criteria for a description. However, taxonomic accounts did not mention C. sleumeriana (e.g. Stevens et al. 2004, Tsukaya 2008). Keng (1974) gives one and a half lines of diagnosis and only relegates to the description and drawing of Sleumer (1967). The potential type specimen (H. Surbeck s.n.) is not cited, neither its location. The type location is missing in Sleumer (1967), too, but in contrast to Keng (1974) Sleumer obviously did see Surbeck s.n., characterizing the material as 'scanty'. Apart from being at least dubious to describe a species without first hand inspection of the type specimen, there are also morphological criteria to dismiss the new species as well as the inclusion of Monotropastrum in Cheilotheca. Wallace (1975), being aware of Keng (1974), convincingly discusses Keng's taxonomic interpretations in an addendum, emphasizing the differences between Monotropastum and Cheilotheca, including the character stressed in Keng's diagnosis: the anthers are erect on filaments in Cheilotheca, they are horizontal in Monotropastrum. In fact, the drawing in Sleumer shows horizontal anthers atop the filaments. Accordingly, Wallace (1975) put Cheilotheca humilis (D. Don) H. Keng and Cheilotheca sleumeriana H. Keng in synonymy with Monotropastrum humlis (D. Don) Hara.