This genus was founded in 1811 by Robert Brown upon Stapelia pulla and S. punctata, Masson, and characterised as having no outer corona (“ staminal corona simple, 5-leaved, with the leaflets toothed on the back ”). But this character must have been made from S. punctata, as S. pulla has a most distinct outer corona. In 1812, Haworth, recognising that S. pulla and S. punctata represented two distinct genera, unfortunately referred S. pulla to Piaranthus, and founded his genus Obesia upon S. punctata, S. decora and S. geminata, Masson, but ascribed to Obesia and Piaranthus identical characters. Matters have been further confused by the erroneous description of Obesia given by Decaisne in DC. Prodr. viii. 661, and by Bentham and Hooker having placed Piaranthus as a synonym of the totally different Podanthes, Haw., whilst finally Dr. Schlechter in Journ. Bot. 1898, 478–479 has united Piaranthus with Caralluma. The genus however is quite distinct from all others and very easily recognised from living plants by the corona and peculiar habit. Some of the species are rather closely allied, and although fairly easy to recognise when alive, I find are difficult to tabulate, whilst dried specimens are exceedingly difficult to discriminate unless exceptionally well dried. In some cases the flowers of the same species vary very considerably in colour and sometimes in ciliation, and distinct varieties might easily be mistaken for different species, but Mr. Pillans informs me that the different variations grow together and are connected by a series of intermediate forms.See also Stapelia fasciculata, Thunb., which may belong to this genus.