The identity of this name has been unclear for some time, but with better knowledge of the Bolivian forest it now clearly applies to a group of Macrocnemum plants from central Bolivia. These plants are similar to Macrocnemum roseum, and have been included in that species previously but do appear distinct. Macrocenumum tortuosum is separated here from Macrocnemum roseum based on its larger flowers, with the corolla tubes 9-11 mm long and the lobes relatively large, 6.5-10 mm long and 4-8 mm wide. Additionally Macrocnemum tortuosum differs in its generally laxer inflorescences with the flowers mostly or all pedicellate and its glabrous inflroescence axes, hypanthia, and calyx limbs, and apparently generally has larger capsules than Macrocnemum roseum. In contrast Macrocnemum roseum characteristically has corolla tubes 5-9 mm long, corolla lobes 3-6 mm long and 2.5-4.2 mm wide, flowers mostly subsessile, and glabrous to densely pubescent inflorescences axes, hypanthia, and calyx limbs. One collector noted that the trunk of Macrocnemum tortuosum was "tortuose", or twisted (Stutter 30), however limited information is available for this character in general for both Macrocnemum tortuosum and Macrocnemum roseum.

However separation of Macrocnemum tortuosum is not entirely clean, with a few plants found in nothern and central Bolivia that appear intermediate between this and Macrocnemum roseum. Occasional plants of Macrocnemum roseum from Beni and La Paz in northern Bolivia also have pedicellate flowers, glabrous inflorescence axes, hypanthia, and calyx limbs, and corollas with the lobes 5-6.5 x 3-4.2 mm wide (e.g., Smith et al. 13765, Beni; Solomon 17400, Maldonado 4463, La Paz). In general in the Bolivian plants the smaller corollas are correlated with inflorescence and flower pubescence and subsessile flowers, while the plants with glabrous laxer inflorescences have relatively larger corollas. This man indicate incomplete separation of these two species, or subsequent hybridization between these, or general variation within the Macrocnemum roseum with one form fixed in the southern populations. Because the flowers and overall inflorescence aspect are quite different in the southern populations, Macrocnemum tortulosum is separated here at least to support study of these plants in more detail. A similar pattern of clinal morphological variation and possible differentiation from northern to central Bolivia is found in several Rubiaceae species, and the Macrocnemum roseum-Macrocnemum tortuosum problem could be a good group for study of this pattern.