What is a European yellow-flowered, gentianaceous (Chlora perfoliata). The whole plant is intensely bitter, and is sometimes used as a tonic, and also in dyeing yellow called?

yellowwort — A European yellow-flowered, gentianaceous (Chlora perfoliata). The whole plant is intensely bitter, and is sometimes used as a tonic, and also in dyeing yellow. (Webster's 1913.)

Sources