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..
Tall perennial aromatic herbs, with large membranous petioled leaves, and terminal loosely panicled racemes of small, yellowish, mostly opposite flowers. Calyx campanulate, short, 10-nerved, 2-lipped, declined in fruit, usually pubescent in the throat; upper lip 3-toothed; lower 2-cleft. Corolla much longer than the calyx, obliquely campanulate, 5-lobed, 4 of the lobes nearly equal, the 5th pendent or declined, fimbriate or lacerate, much larger, appearing like a lower lip. Anther-bearing stamens 2, not declined, much exserted, coiled before antithesis; bases of the filaments connected by a woolly ring; anthers 2-celled, or the sacs at length partially confluent. Ovary deeply 4-parted. Nutlets smooth, globose. [Named for Peter Collinson, 1693-1768, an English botanist, and correspondent of Linnaeus.]
Three species, natives of eastern North America, the following typical.
Collinsonia canadensis L. Sp. Pl. 28. 1753.
Stem stout, erect or ascending, branched, 2°-5° high, glabrous, or glandular-pubescent above. Leaves ovate or ovate-oblong, acuminate at the apex, narrowed, obtuse or sometimes cordate at the base, the lower slender-petioled, 6'-10' long, the upper nearly sessile, much smaller, all coarsely dentate; racemes numerous, in terminal panicles sometimes 1° long; pedicels ascending, 3"-6" long in fruit, subu-late-bracteolate at the base; flowers lemon-scented; calyx-teeth subulate, those of the lower lip much longer than the upper; corolla light yellow, 5"-7" long; anther-bearing stamens 2, the upper pair rudimentary; fruiting calyx ribbed, 3"-4" long.
In moist woods, Quebec and Ontario to Wisconsin, south to Florida, Alabama and Arkansas. Root large, thick, woody. Knob-or horse-weed. Knob-grass or -root. Collin-son's-flower. Rich leaf. Stone-root. July-Oct.