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.
Herbs or undershrubs with the flowers in bracteate spikes or racemes of whorls. Calyx tubular-campanulate, equally or unequally 5-toothed. Corolla-tube short, naked within; limb unequally 5-lobed, the 2 uppermost very short, and the centra] one of the 3 lower ones largest and elongated. Stamens 4, exceeding the corolla, the lower 2 longest. The species are numerous and widely dispersed. One, T. Scorodonia, Wood-Sage, is a common British plant. It has Sage-like leaves and one-sided terminal racemes of small yellowish white flowers. Two or three other species are met with in some parts of England, but they are very rare, and probably escapes from old gardens, having been formerly cultivated as medicinal herbs, under the name of Germander. The generic name is of a classical origin.
T. Pyrenaicum is a distinct species with rotundate crenate petiolate leaves and clustered terminal purple and white flowers.
Ajuga reptans, common Bugle, is exceedingly abundant in many parts of Britain. It is a creeping almost glabrous plant with ovate crenate leaves and loose bracteate spikes of blue, white or reddish flowers, in which the short upper lip of the corolla is nearly entire. Some of the varieties are grown in gardens.