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 erect branching herbs, some western species shrubby, with lanceolate oblong or linear entire or slightly repand leaves. Flowers small, or middle-sized, pink, blue, purple, or white, paniculate, or in axillary loose or dense cymes. Calyx campanulate, very unequally 5-lobed in our species, the lobes ovate or lanceolate, the 3 upper much longer than the 2 lower. Corolla-tube slender, exserted or included, the limb somewhat oblique and deeply 5-cleft into oblong more or less declined segments. Stamens 4, didynamous, ascending, curved, the anterior pair the longer, the filaments filiform, spirally coiled in the bud, long-exserted; anther-sacs divaricate, more or less confluent at the base. Ovary deeply 4-lobed; style 2-cleft at the summit. Nutlets obovoid, reticulated. [Greek, hair-stamen, referring to the slender filaments.!
About 10 species, natives of North America. Type species: Trichostema dichotomum L. Leaves oblong or lanceolate; plant minutely viscid-pubescent.
1. T. dichotomum.
Leaves linear; plant puberulent or glabrous.
2. T. lineare.
Trichostema dichotomum L. Sp. Pl. 598. 1753.
Annual, minutely viscid-pubescent; stem slender, rather stiff, much branched, 6'-2° high, the branches spreading or ascending. Leaves oblong or oblong-lanceolate, membranous, obtuse or subacute at the apex, narrowed at the base into short petioles, 1'- 3' long, 3"-10" wide, the upper gradually smaller; flowers paniculate, 6'-9" long, borne 1-3 together on 2-bracteolate peduncles; calyx oblique, very unequally 5-lobed, the 3 upper lobes much longer and more united than the 2 lower ones; corolla blue, pink or rarely nearly white, the limb longer than the tube; stamens blue or violet.
In dry fields, Maine to Florida, Vermont, Pennsylvania, Missouri and Texas. The lateral flowers become inverted by torsion of the pedicels. July-Oct.
T. brachiatum Lam. Encycl. 8: 84. 1808. Not L. 1753. Trichostema lineare Nutt. Gen. 2: 39. 1818.
Puberulent or glabrous, not viscid or scarcely so; stem very slender, at length widely branched, 6'-18' high, the branches ascending. Leaves linear, obtuse or subacute, sessile or very short-petioled, 1/2' - 2' long, 1"-2" wide, sometimes with smaller ones or short leafy branches in their axils; flowers very similar to those of the preceding species, sometimes larger.
In sandy fields and dry pine barrens, Connecticut to Georgia and Louisiana, mostly near the coast. July-Aug.