Siona classification of yagé is seen to be more complex than that of botany and depends on the conjunction of b otanical features, chemical effects of the mode of preparation, and the cultural suggestion of the visions experimented. The impoortance of the influence of culture on the visionary state induced by the chemical composition must be examined if we are to deepend our understanding of the affects of hallucinogens. The Siona, as ethnochemists, have extensive knowledge in producing hallucinogenic brews, using different parts of the plants, a large varienty of admixtures, and different modes of preparation. However, a direct link between the plant selected, its preparation and its visionary effects cannot be made, since cultural mechanisms enter to guide the experience. I believe that further exploration between this conjunction of botany-chemistry-culture warrents further investigation.