Tumors in plants. Crown gall, a plant tumor, is caused by a bacterium (Agrobacterium tumefaciens) that carries a tumor-inducing plasmid (Ti plasmid).

[From M. Escobar et al., Proc. Natl. Acad. Sci. U. S. A. 98:13437–13442, 2001. Copyright © 2001 National Academy of Sciences, U. S. A.]