it grows, but even flee from the traveler who carries a piece of it in his hand". A. pfeiferi, A. rugosa, and A. trilobata are also used in folk medicine to treat snakebites. Toxicity and carcinogenicity In 1993, a series of end-stage renal disease cases was reported from Belgium associated with a weight loss treatment, where Stephania tetrandra in a herbal preparation was suspected of being replaced with Aristolochia fangchi. More than 105 patients were identified with nephropathy following the ingestion of this preparation from the same clinic from 1990 to 1992. Many required renal transplantation or dialysis. Aristolochia is a component of some Chinese herbal medicines. Aristolochia has been shown to be both a potent carcinogen and kidney toxin. Herbal compounds containing Aristolochia are classified as a Group 1 carcinogen by the International Agency for Research on Cancer. Epidemiological and laboratory studies have identified Aristolochia to be a dangerous kidney toxin; Aristolochia has been shown to be associated with more than 100 cases of kidney failure. Furthermore, it appears as if contamination of grain with European birthwort (A. clematitis) is a cause of Balkan nephropathy, a severe renal disease occurring in parts of southeast Europe. In 2001 the UK government banned the sale, supply and importation of any medicinal product consisting of or containing a plant of the genus Aristolochia. Several other plant species that do not cause themselves kidney poisoning, but which were commonly substituted with Aristolochia in the remedies, were prohibited in the same order. Aristolochic acid was linked to aristolochic acid-associated urothelial cancer in a Taiwanese study in 2012. In 2013, two studies reported that aristolochic acid is a strong carcinogen. Whole-genome and exome analysis of individuals with a known exposure to aristolochic acid revealed a higher rate of somatic mutation in DNA. Metabolites of aristolochic acid enter the cell nucleus and form adducts on DNA. While adducts on the transcribed DNA strand within genes are detected and removed by transcription-coupled repair, the adducts on the non-transcribed strand remain and eventually cause DNA replication errors. These adducts have a preference for adenine bases, and cause A-to-T transversions. Furthermore, these metabolites appear to show a preference for CAG and TAG sequences. Garden history Due to their spectacular flowers, several species are used as ornamental plants, notably the hardy A. durior of eastern North America, which was one of John Bartram's many introductions to British gardens; in 1761