From a hydraulic perspective, mistletoes show one of the most interesting examples of xylem structure. These plants can develop a u201cchimeric sap transport systemu201d, which comprises cells of both host and parasite wood.Additionally, these parasites may cause an overload for the sap transport capacity, since they usually bear stomata in both sides of the leaf, showing poor gas exchange control. Therefore, the capacity to regulate and adjust the transport system is a key factor in determining the probability of survival of a parasitic plant. This work investigated whether and how the wood formation of some mistletoes varies within the stem topology. Three Loranthaceae species were selected for this study, all possessing relatively large dimensions, either radially or axially and occurring naturally in Brazil. Psittacanthus robustus is a woodrose-forming shrub with thick branches up to 3m long and 4 cm in diameter; Tripodanthus acutifolius, a lianescent/tree species that reaches several meters long; and Struthanthus flexicaulis, a decurrent shrub with very flexible and long stems (up to 4 m). The length of both vessel elements and fibres was observed to stabilize about 2mm away from the pith. Thus, our data suggest that at least for the thickest stems (P. robustus and T. acutifolius), the secondary xylem indeed reaches the state of mature wood in relatively thin diameter, which makes the comparison with other species viable. In the case of Struthanthus flexicaulis, there is no clear change of pattern along the stem axis. So far, our data suggest that one of two things might be occurring: i) there is a reduction on the mean vessel diameter along the stem, which would lower the risk of cavitation by raising the resistance of that part of the system; ii) there is an increase in the total vessel density, which generates both an increase of conductivity of the system, but primordially its redundancy.Both of those characteristics would ultimately serve the same objective: to increase the hydraulic safety in the parts that theoretically undergo highest hydraulic tension. Furthermore, changes in cell size were observed in a periodical fashion. In short, these plants seem to possess a very plastic xylem, capable of adapting its structure and organization to better absorb nutrients from the host without killing it.