Evidence from published work is first reviewed to show that cationic, neutral, and anionic complexes of the uranyl ion are available to plants growing in uranium-enriched environments. The results of a study on the uptake of uranyl ions by the lichen Cladonia rangiferina L. Wigg. are then presented. Uptake was examined from three different uranyl solutions each predominantly containing a single species: namely, the cation [Formula: see text] (in distilled water), the neutral 1:1 complex with phthalate (UO2L), and the anionic complex of oxalate [Formula: see text]. Uptake decreased along the chemical speciation series: cation [Formula: see text] neutral species [Formula: see text] anion. Maximum observable capacities for this series were, respectively, 49, 17, and 1.6 μmol/g for 1-g samples in 100 mL containing 840 μmol of total uranium. The [Formula: see text] uptake curve was observed to be monophasic, while biphasic patterns appeared to apply for the phthalate and oxalate buffers. Heat-killed tissues showed marginally higher uptake capacities than live material.