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.
Herbaceous or shrubby plants, frequently furnished with immersed glands of aromatic fragrant oil. Stems usually 4-angled. Leaves opposite or verticillate, simple or compound. Flowers in axillary cymes or solitary or capitate. Calyx inferior, tabular, ribbed, 5- or 10-toothed or bilabiate. Corolla usually bilabiate, the upper lip overlapping the lower in bud. Stamens 4 and didynamous, or only 2. Fruit composed of 4 (rarely fewer) 1-seeded nutlets enclosed in the persistent calyx. Seeds erect, with little or no albumen. A very large and very natural assemblage of plants, comprising about 2,500 species, chiefly inhabiting temperate and tropical countries. The order is abundantly represented in Britain and in the herb garden. Sage, Salvia officinalis; Spearmint, Mentha viridis; Peppermint, M. piperita; Thyme, Thymus vulgaris; Marjoram, Origanum vulgare; and Basil, Ocymum Basilicum, are amongst the most familiar.