Butterwort; a genus of the monogynia order, belonging to the diandria clas of plants. There are four species; of which the most remarkable is the vulgaris, or common butterwort, growing commonly on bogs or low moist grounds in England and Scotland. Its leaves are covered with foxtail upright pellucid prickles, secreting a glutinous liquor. The flowers are pale red, purple, or deep violet colour, and hairy within. If the fresh gathered leaves of this plant are put into the strainer through which warm milk from the cow is poured, and the milk set by for a day or two to become acetic, it acquires a consistence and tenacity, and neither whey nor cream separate from it. In this state it is an extremely grateful food, and as such is used by the inhabitants of the north of Sweden. There is no further occasion to have recourse to the leaves; for half a spoonful of this prepared milk, mixed with fresh warm milk, will convert it to its own nature, and this again will change another quantity of fresh milk, and so on without end. The juice of the leaves kills lice; and the common people use it to cure the cracks or chops in cows' udders. The plant is generally supposed injurious to sheep, by occasioning in them that disease called the rot. But from experiments made on purpose, and conducted with accuracy, it appears, that neither sheep, cows, goats, horses, or swine, will feed upon this plant.

Wherever this plant, called also Yorkshire fumicle, is found, it is a certain indication of a boggy soil. From the idea that the country people have of its noxious operation on sheep, this plant has been called the white rot; since as they imagine it gives them the rot whenever they eat it, which they will not do but from great necessity.

The Laplanders, like the Swedes with the milk of cows, receive that of the rein-deer upon the fresh leaves of this plant, which they immediately strain off and set aside till it becomes somewhat acetic; and the whole acquires in a day or two the consistence of cream without separating the serum, and thus becomes an agreeable food. When thus prepared, a small quantity of the same has the property of rennet in producing the like change on fresh milk.