Do both Butea and Calanthe have just two species?
Calanthe Calanthe – commonly abbreviated Cal. in horticulture – is a widespread genus of terrestrial orchids (family Orchidaceae) with some 200 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".