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..
Herbs (some tropical species shrubs), with alternate or basal leaves and racemose spicate or paniculate, often leafy bracted, red, yellow, blue or white flowers. Calyx-tube turbinate, hemispheric or ovoid, adnate to the ovary. Corolla-tube straight, oblique or incurved, divided to the base on one side, 2-lipped in our species, the lobe on each side of the cleft erect or recurved, turned away from the other three which are somewhat united, the sinuses inclining to extend to the base of the corolla at maturity so as to divide it into 5 petals. Stamens free from the corolla-tube, monadelphous, at least above, two or all the 5 anthers with a tuft of hairs at the tips, three of them usually larger than the other two, all united into a tube or ring around the style. Ovary 2-celled, the 2 placentae many-ovuled; stigma 2-lobed or 2-cleft. Capsule loculicidally 2-valved. [Named after Matthias de L'Obel, 1538-1616, a Flemish botanist.]
About 250 species, of wide geographic distribution. Besides the following, some 16 others occur in the southern and western United States. Type species: Lobelia Dortmanna L.
*Aquatic; stem simple, nearly naked; flowers light blue. Leaves terete, hollow, obtuse, tufted at the base.
1. L. Dortmanna.
Leaves flat, linear-oblong or spatulate, entire or glandular-denticulate.
2. L. paludosa.
** Terrestrial plants of wet or dry soil; stems leafy. 1. Corolla-tube 5"-12" long. Flowers bright scarlet (rarely white); corolla-tube 10"-12" long.
3. L. cardinalis.
Flowers blue, white, or blue and white; corolla-tube 5-7 long. Leaves ovate, lanceolate, or the lower ones obovate. Leaves glabrous or sparingly pubescent.
Calyx-lobes hirsute; sinuses with large deflexed auricles.
4. L. syphilitica.
Calyx-lobes glabrous or glandular, usually without auricles. Leaves ovate to ovate-lanceolate, spreading1.
5. L. amoena.
Leaves linear to narrowly lanceolate, erect.
6. L. elongata.
Leaves densely puberulent; calyx hirsute; auricles small.
7. L. puberula.
Leaves elongated-linear, strongly glandular-denticulate.
8. L. glanduosa 2. Corolla-tube only 2"-4" long. Stems mostly simple; flowers in terminal spike-like racemes. Sinuses of the calyx without auricles.
9. L. spicata.
Sinuses of the calyx with reflexed subulate auricles.
10. L. leptostachys.
Stems mostly paniculately branched; flowers in loose racemes. Stem stout, pubescent; leaves ovate or oblong, dentate.
11. L. inflata.
Stems slender, glabrous; stem-leaves narrow, the basal wider.
Pedicels mostly longer than flowers, 2-bracteolate near the middle.
12. L. Kalmii.
Pedicels not longer than flowers, not bracteolate, or only so at the base. Corolla 21/2"-3 1/2" long: calyx-tube hemispheric in fruit.
Corolla 41/2"-51/2" long; calyx-tube turbinate.
14. L. Canbyi.