After the investigation I conducted by the Aguarunas, it is possible to say that they use two different plants to make Natem: one of which is used is Banisteriopsis, and the other is Yajé, whose leaves are used only. These leaves I own have exactly the same characters as the Yajé leaves whose drawing, published in the Reinburg article: “Contribution to the study of toxic drinks of the Northwest Indians of the Amazon”, was made according to a specimen, without flowers, harvested by the author. Among these characters, the most striking are the long-cuspided top and, above all, the secondary nervous that connect with arcs not on the very edge of the leaves, but more inside, leaving between them and this one for submarginal additional nervous. Gagnepain to whom Reinburg had given his specimen for his determination compared it to several Amazonian species and ultimately analysis at Prestonia amazonica Benth. that Spruce had seen the use of the Banisteriopsis in the Uaupe, and found it near this species. I myself compared my specimen to Prestonia amazonica, which is located at the herbier of Paris, and to the drawing of the copy, picked up by Spruce and kept at Kew's herbier, sent to Gagnepain; then I compared it to other Apocynacees of this kind. I found on any of them the type of nervous of the specimen that was brought to me by an Aguaruna; in addition, the latter belongs to a shrub and not to a bine. But further examination may even make doubt about its belonging to the Apocynaceae family. The branches have clear traces of stipules and, moreover, the study of a cross-section of a rod has shown the lack of an internal phloem. These different examinations are only superficial, and only a thorough study of morphological and anatomical characters and a chemical analysis can inform the problem of the botanical identification of the Yajé and its possible hallucinogenic power.