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. C. coelestis, syn. C. tuberosa. - The prettiest of the hardy species. It is a dwarf much-branched plant with oblong-lanceolate leaves and clusters of blue or white flowers issuing from a spathe. It is a native of Mexico, and rather tender.