A preliminary study on the carcinogenicity of the common fern Onychium contiguum.

Onychium contiguum (Family Cryptogrammaceae) is a common terrestrial fern in the Himalayas and in many other parts of the world. It is also present on the pastures in areas where grazing animals suffer from bovine urinary bladder cancer. This fern is occasionally grazed by animals and in some areas it is present as a contaminant in grasses stored for winter feeding. Certain species of the genus Onychium are used in folk medicine. Long-term exposure of experimental animals to O. contiguum appeared to cause tumours of the ileum. urinary bladder and mammary glands.