Thomas G. HARTLEY & David J. MABBERLEY
Picrella Baill., based on the cultivated P. trifoliata Baill., is an earlier name for the New Caledonian genus Zieridium Baill., and not referable to a Mexican plant as previously assumed. A revision of the genus is presented. Three species are recognised: P. glandulosa T.G. Hartley, sp. nov., P. ignambiensis (Guillaumin) T.G. Hartley & Mabb., comb. Nov., and P. trifoliata, comprising three varieties including var. gracilis (Baill.) T.G. Hartley & Mabb., comb. et stat. nov., and var. gracillima T.G. Hartley, var. nov.