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 genus of tropical herbs and shrubs, valuable for the brilliantly-coloured foliage of the species in general cultivation. The flowers are small and inconspicuous, and borne in terminal spikes of verticillasters. Calyx campanulate; limb 5-toothed or bilabiate, recurved in fruit. Corolla with a slender tube and bilabiate limb, upper lip 3- or 4-lobed, lower lip entire, frequently concave, and enclosing the stamens. The species are natives of tropical Asia and Africa, and consequently tender, and only suitable for sheltered warm gardens in Summer. The name is derived from a sheath, the filaments being united at the base.
C. Blumei, from Java, appears to have been the first introduced of the set with ornamental foliage. It is an erect rather succulent herbaceous plant with large ovate-acuminate toothed leaves of a pale green marbled or spotted with purple-brown, and small blue and white flowers. Somewhat recently two other species or forms have been introduced from the Pacific Islands, namely, G. Veitchii and G. Gibsoni. The foliage of these is variegated with crimson, purple, and green, and by intercrossing these with G. Blumei in various ways, many very magnificent varieties have been obtained. In some the colours are of dazzling brightness, and beautifully contrasted. Some of the first were raised in the gardens of the Horticultural Society at Chiswick; and now every year produces its quota of new ones.