There are no floral differences between the Peruvian and Venezuelan collections, and Guayana material easily bridges the obscure gap in leaf base characters. Of more import is the distinctness from other related species. Flower-mery in the group is a difficult character to use; M. puberula Cogn. seems predominantly 4-merous (as shown also in the Flora Brasiliensis illustration, despite Cogniaux' 5-merous description), while M . brevipes Benth. seems to be 4-5(-6, fide Gleason's notes)-merous. The poorly known M. kappleri Naud. and M. fragilis Naud. are both suggestive of this relationship; they apparently differ from the pubescent species in the glabrous stem internodes and leaves and (except for M. puberula) the smaller flowers.