A Toxic Principle in the Leaves of Ailanthus

The presence of a substance that was toxic to other tree seedlings was demonstrated in aqueous extracts of foliage from Ailanthus altissima (Mills) Swingle. 2. The effect of concentration of, and the response to, this extract was tested on thirty-five species of gymnosperms and on eleven species of angiosperms. Members of all species, with the exception of those of Fraxinus americana L., were adversely affected.