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.
Annual or perennial herbs with opposite leaves and spiked or capitate bracteate whorls of flowers. Calyx tubular, straight, 5-toothed, the upper tooth usually largest. Corolla-tube inflated at the throat; limbs bilabiate, upper lip concave, lower lip 3-lobed. Stamens 4. There are about thirty species, in temperate and warm regions of the north. The name is a compound of a dragon, and a head, literally dragon's head, from the shape of the corolla.
1. D. peregrinum. - A handsome decumbent perennial species. Leaves lanceolate, remotely toothed and mucronate, tomentose beneath. Flowers violet-blue, spotted on the lips, solitary and axillary, appearing in Autumn. A native of Siberia.
2. D. Argunense, syn. D. Altaicum. - This is a more erect species, from 1 to 2 feet high, with lanceolate entire glabrous leaves and large blue flowers in spikes of whorls. A native of Siberia, flowering in Summer.
3. D. Moldavicum. - A fragrant annual about 18 inches high. Leaves oblong-lanceolate, sharply-toothed. Flowers small, blue, in the axils of the upper leaves.
D. Ruyschianum has also small blue flowers with hairy-calyces.
Cedronella is very near the last genus, except that the anther-cells are parallel instead of diverging. 0. cana is a hoary perennial with small ovate-cordate leaves and bright red flowers; C. Mexicana a more robust species destitute of hoary down, with interrupted spikes of less brightly-coloured flowers. Both are natives of Mexico.
Melittis Melissophyllum, including M. grandiflora, Bastard Balm, is one of our handsomest native Labiates. It is an erect perennial with ovate-oblong crenate slightly hairy leaves and few-flowered axillary whorls of white and pink or purple showy flowers. The variety grandiflora is very handsome. This plant is remarkable for the large campanulate membranous calyx and nearly flat upper lip of the corolla. It is only found in the southern parts of England.