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.
A small European genus remarkable for the smooth glaucous stem-clasping foliage of its species. They are with one or two exceptions of annual duration. The flowers are in one-sided leafy racemes, yellow or yellow and purplish violet. Corolla tubular; throat naked. Anthers sagittate, cohering at the base. But the principal distinctive character is in the fruit, which is composed of 2 free 2-celled nuts. The name is from wax, and a flower, in allusion to the fondness of bees for these flowers, and hence the English name Honey-wort.
1. C. major. - A branching annual about a foot high. Leaves glaucous, oval, stem-clasping, minutely toothed and clothed with rough white tubercles. Corolla pale yellow, violet and yellow, or dull violet, constricted at the mouth and shortly 5-toothed, the teeth reflexed.
C. minor is of smaller growth, with similar auricled leaves and smaller yellow flowers, sometimes with 5 brownish spots. Corolla divided about a third of the length into 5 subulate erect teeth. C. retorta has yellow and brown flowers with a curved corolla, and the leaves covered with silvery blotches.