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..
Annual or perennial, often stoloniferous herbs, mostly with dentate leaves, and rather large verticillate-clustered flowers in terminal spikes, or in the upper axils. Calyx ovoid or campanulate, 10-many-nerved, 5-toothed or 5-lobed, the teeth or lobes nearly equal. Corolla-limb 2-lipped, the upper lip short, truncate or emarginate, the lower spreading, with 2 small lateral lobes and a much larger emarginate or 2-cleft middle one. Stamens 4, didynamous, somewhat exserted beyond the upper lip of the corolla, the anterior pair the longer; anthersacs divergent, only slightly confluent at the base. Ovary not deeply 4-lobed. Nutlets obovoid, rugose-reticulate. [Greek, without a yoke; from the seeming absence of the upper lip of the corolla.]
About 40 species, natives of the Old World. Type species: Ajuga reptans L. Sparingly pubescent, or glabrous, stoloniferous.
1. A. reptans.
Pubescent with long hairs, not stolonilerous.
2. A. genevensis.
Ajuga reptans L. Sp. Pl. 561. 1753.
Perennial, sparingly pubescent or glabrous, producing slender creeping stolons sometimes 1° long; stem erect, rather stout, 6-15' tall. Basal leaves tufted, obovate, rounded at the apex, crenate or undulate, l'-3' long, tapering into margined petioles; leaves of the stem oblong or oblanceolate, much smaller, sessile or nearly so, those of the stolons mostly petioled; upper flower-clusters often forming a short spike, the lower commonly distant and axillary; corolla blue or nearly white, about i' long.
Ajuga genevensis L. Sp. Pl. 561. 1753- Perennial, not stoloniferous; stems usually several from the root, ascending, rather stout, long-pubescent. Leaves long-pubescent, the basal ones long-petioled, spatulate or oblanceolate, obtuse, sparingly toothed or entire, 2'-4' long, the upper sessile, obovate to ovate, usually coarsely dentate, much smaller; bracts pubescent, the upper shorter than the flowers; inflorescence mostly dense; corolla 1/2'-3/4 long.
In fields and waste grounds, Maine to New York and Pennsylvania. Adventive from Europe. May-July.