Some authors (Burger, 1971; Görts in van Proosdij et al., 2007; Sutherland, 2008) have suggested that P. elongata Kunth is a synonym of P. macrostachyos (Vahl) A.Dietr. However, most authors (see references provided by Tropicos) accept them to be different species. Although both species show a similar habit, their habitat preferences differ. P. elongata is a terrestrial, creeping or climbing plant, while P. macrostachyos is a pending epiphyte growing on ant nests. The leaves of P. elongata are somewhat fleshier than the leathery ones of P. macrostachyos, but this difference is only apparent in living plants, not in herbarium specimens. Diagnostic is the morphology of the floral bracts, clearly fimbriate in P. macrostachyo but never in P. elongata.