122 British plants of the genus Symphytum were investigated cytologically. White-flowered diploid (2n=24) and white- and purple-flowered tetraploid (2n=48) plants of S. officinale occur in Britain. S. X uplandicum. the hybrid between S. officinale (2n = 40 or 2n = 48) and S. asperum (2n = 32) is variable, but two types can be distinguished, the first of which has 2n = 36, purple flower-buds and purple (or blue-purple) corollas, the second 2n =40, pink flower-buds and pink corollas, which turn blue when the flowers age. The way in which these hybrids arose is discussed.