Bistella Adans. versus Vahlia Thunb. (Vahliaceae)

The somewhat peculiar genus Vahlia Thunb. (1782) was formerly regarded as an anomalous member of the Saxifragaceae, but in 1959 it was segregated as the monotypic family Vahliaceae by Dandy (in Hutchinson, Fam. Fl. Pl. ed. 2, 1: 461). The genus includes about three species, all of them highly variable in stature, flower size, and indumentum; this has resulted in the description of more than twenty “species”, whose names now appear in synonymy. This note, however, is chiefly concerned with the generic name, since it appears that Vahlia Thunb. is not correct under the Code and must be replaced by Bistella Adans. (1763). In the synonymy under the new combinations, all the relevant names so far traced are included, but it may well be that an experimental approach to the problem of specific and infraspecific limits and the taxonomic value of the characters hitherto relied upon for differentiation would result in considerable changes. Bistella Adans. (1763) was cited in the form “ Bistella Lippi 243 – Ascyroides Lippi” and the name than fell into abeyance until it was resuscitated by Delile in 1826. He described plants collected by Cailliaud, and identified a number of them with those of Lippi. In particular, he identified Lippi 243 (and 244) with the Cailliaud plant which he named “ Bistella geminiflora Delil. (Descript, des plantes découv. par M. Cailliaud, pl. II. fig. 4). – Ascyroides Lippi (Manusc. nos. 243 et 244).” It must be emphasized that the taxonomic identification of “ Bistella Del.” with Vahlia Thunb. has never been questioned, but the identity of Adanson’s Bistella with Bistella geminiflora Del. has been overlooked; this species, as represented by Lippi’s plant, is the type of the generic name Bistella Adans