Do both Butea and Calanthe have just two species?
Butea Butea is a genus of flowering plants belonging to the pea family, Fabaceae. It is sometimes considered to have only two species, "B. monosperma" and "B. superba", or is expanded to include four or five species.
Banksia ser. Dryandroideae Banksia" ser. "Dryandroideae is a taxonomic series in the plant genus "Banksia". First published by Carl Meissner in 1856, the name has had two circumscriptions. As presently circumscribed it is monotypic, containing only "B. dryandroides".