As we were preparing for our departure, Dr. Roser unexpectedly packed up a number of objects of natural history and scientific interest, which he kindly presented to the Imperial expedition as a _souvenir_ of Genaaden Dal. Besides these, there were also given to us two valuable little books,--one a small work upon the Nicobar Islands, written about the beginning of this century by a Moravian brother of the name of Gottfried Hensel; the other a treatise composed by the excellent Dr. Roser himself, upon the pharmaceutics and natural history of Genaaden Dal. With respect to the various substances chewed as stimulants, or intoxicants, by the Hottentots, in order to deprive themselves of sensation, or rouse themselves to a state of high excitability, we found the following particulars in this interesting essay. That most in use is composed of the bruised leaves of the "_Leonotis Leonurus_." This plant, which grows in great quantity in and beyond the Genaaden Dal, is called by the natives "Dagga," as also frequently, "Tacha or Takka," and this variation in pronunciation is very probably the reason that we find in Berghaus's "_Völker des Erdballs_" (Races of the Globe), this celebrated smoke-weed, marked as "Donha." What the same author says of certain stimulating properties of the plant may well be considered as an exaggeration. It is curious how the properties of this plant seem to be inextricably mingled with the destinies of the Hottentots. In many places it has been extirpated, in order more readily to wean the aborigines from the practice of chewing: at other places again, "_Leonotis Leonurus_" is expressly planted in order to attract the Hottentots, and so supply any deficiency in hands for labour, reckless of the moral consequences. Another narcotic, and the most widely prevalent, is the wild hemp (_Canabis Sativa_), the dried leaves of which are smoked by the natives. Dr. Juritz, one of the most respectable apothecaries in Cape Town, assured us he had been compelled, during a previous residence at Stellenbosch, where he was engaged in his business, to keep always on hand in his store a large quantity of wild hemp for sale to the natives. The poison with which the Bushmen tip their arrows, rendering them such dangerous and terrible weapons, is extracted from the "_Cestrum venenatum_."[53] [Footnote 53: The Dyaks of Borneo poison their arrows with the juice of _Strychnos Tieuté_ and _Antiaris Toxicaria_ (Upas).]