EVERYONE who is interested in agriculture is aware that liver-fluke or sheep-rot is popularly associated with one or another of our common plants. Halliwell gives “sheep-killing” as a name for “the herb pennywort”. In Britten and Holland (“English Plant Names”) we find sheep-rot, sheep-bane, and other similar terms, and we are told that such plants as Pinguicula vulgaris, L., and Hydrocotyle vulgaris, L., are known by these popular names because of a supposition that these plants cause the liver-rot in sheep, which disease is often prevalent on wet land where the plants grow. The authors further inform us that “It is now ascertained that the liver-fluke, which always accompanies rot in sheep, exists in one of its stages as a parasite in the bodies of small water snails, which, in wet weather, creep upon the leaves of marsh plants, and are eaten by the sheep with the herbage. It is therefore with some reason that such names as ‘Flowkwort,’ ‘Sheep-killing Penny-grass,’ and ‘Sheep-rot’ have been given to these marsh plants”.