In the accounts given by travellers of the festivities of the South American Indians, and of the incantations of their Medicine- men, frequent mention is made of powerful drugs used to produce intoxication, or even temporary delirium. Some of these narcotics are absorbed in the form of smoke, others as snuff, and others as drink ; but, with the exception of tobacco, and of the fermented drinks prepared from the grain of maize, the fruit of plantains, and the roots of Manihot utilissima , M. Aypi, and a few other plants, scarcely any of them are well made out. Having had the good fortune to see the two most famous narcotics in use, and to obtain specimens of the plants that afford them sufficiently perfect to be determine d botanically, I propose to record my observations on them, made on the spoL The first of these narcotics is afforded by a climbing plant called Caapi in North Brazil and Venezuela , but Ayahuasca, or Dead-man's Vine, about the eastern foot of the Andes of Peru and Ecuador. It belongs to the family of Malpighiaceae; and I drew up the following brief description of it, from living specimens , in November, 1853.