Laburnum (Cytisus Laburnum), a favourite tree in our gardens, belonging to the pea tribe and to the same genus as the broom (q.v.). It is a native of the south of Europe, and was introduced into England in the 16th century. The heart-wood is very dense and dark-coloured, resembling ebony, and is used in turnery. The leaves have a white down beneath, which, with the downiness and many-seeded character of the pods, distinguishes the tree from the so-called Scotch laburnum (C. alpinus). C. Adami is a hybrid between the laburnum and the shrubby C. purpureas, perhaps originating in a graft (q.v.). The roots and leaves of laburnum are poisonous, and the seeds dangerously so. They contain two poisonous alkaloids, cytisin and laburnin, and have a powerful emetic action.