This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol3", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Perennial herbs, or low shrubby creeping plants, with small mostly entire leaves, and small purple flowers clustered in terminal glomerules, or in the axils of the leaves. Calyx ovoid, villous in the throat, 10-13-nerved, 2-lipped, the upper lip erect-spreading, 3-toothed, the lower 2-toothed, its teeth long and slender. Corolla-limb 2-lipped, the upper lip erect, emarginate, the lower spreading, 3-cleft. Stamens 4, more or less didynamous, mostly ex-serted; anthers 2-celled, the sacs parallel or divergent. Ovary deeply 4-parted; style 2-cleft at the summit. Nutlets ovoid or oblong, smooth. [Greek, incense.]
About 50 species, natives of the Old World, mostly European. Type species: Thymus vulgaris L.
Thymus Serpyllum L. Sp. Pl. 590. 1753.
Stems more or less pubescent in lines, very slender, procumbent, tough, much branched, 4'-12' long, commonly forming dense mats. Leaves oblong or ovate-oblong, petioled, obtuse at the apex, usually narrowed at the base, entire, glabrous, or sometimes ciliate, 2"-5" long; bracts similar to the leaves, but smaller; flowers numerous in verticillate clusters crowded in dense short terminal spikes, or also in the upper axils; calyx distinctly 2-lipped, the tube usually pubescent and the teeth ciliate; corolla longer than the calyx.
In thickets, woods, and along roadsides, Nova Scotia to southern New York and North Carolina. Naturalized from Europe. Native also of Asia. June-Sept. Old English names, brotherwort, hillwort, penny-mountain, shepherd's-thyme.