This section is from the book "Handbook Of Hardy Trees, Shrubs, And Herbaceous Plants", by W. Botting Hemsley. Also available from Amazon: Handbook of hardy trees, shrubs, and herbaceous plants.
1. T. coerulea, better known as Didiscus caeruleus. - This is the only familiar ornamental annual species of this family. It grows from 1 to 2 feet high. Leaves triternately divided into linear segments. Flowers bright blue. Fruit tubercular.