Phitopis was published for a species from the Andes of Peru, which was poorly documented. The genus was not well known for some time, due in large part to poor documentation of the flora of that region, and to confusion about the identity of this genus.
The form of the stipules of Phitopis was described inaccurately in the protologue, and that generated some confusion about the identity and relationships of this genus. The stipules are calyptrate (i.e., fused into a conical cap) and caducous, falling off as a complete structure or sometimes fragmenting. However the stipules were originally described by Hooker as "utrinque 2, basi discretae, erecti" ("always 2, separated at the base, and erect"). This description seems to be based on the conical stipules of the axillary buds, which are frequently shortly and symmetrically developed on most of the nodes, while the stipules of the main stems fall off so rapidly that sometimes none are readily visible. The figure in the protologue (t. 1093) shows four such buds per node, which may be anomalous development of the stem illustrated, or may be inaccurate; all modern specimens studied have consistent two axillary buds per node, pers. obs.). A few subsequent authors correctly identified the species of Phitopis (e.g., Standley, 1936: pp. 67-68), but the name Phitopis multiflora was also incorrectly applied to various species that appeared to have two free stipules or the genus was considered so poorly known that it was not clear what this species was. The reportedly paired free stipules were cited and even illustrated for this genus by subsequent authors (e.g., Robbrecht 1988, fig. 14A, p. 54, and references cited there), and based on this character the genus was considered of unclear or perhaps very primitive position within the Rubiaceae. Standley only described the stipules as "caducous", with no additional information about their form even though he (correctly) included another species in Phitopis and thus had access to additional study materials.
Standley (1936) included Phitopis in the Rondeletieae, which in his circumscription included a heterogenous assemblage of genera but did also include Bathysa. Kainulainen et al. (2010) studied several of the genera that were included in Standley's Rondeletieae, and found Phitopis and several species that were classified in Bathysa (but not the type of Bathysa) to be related to each other. This combined group takes the name Schizocalyx Wedd., and was surveyed by Taylor et al. (2011). See the Rubiaceae Project page for Schizocalyx for more detailed information about this group.
C.M. Taylor, III 2012