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 or rarely annual, erect or diffuse herbs, with opposite entire leaves, or some of the upper ones alternate, and large blue purple red or white flowers, in terminal cymes or cymose panicles. Calyx tubular or tubular-campanulate, 5-ribbed, 5-cleft, the lobes acute or acuminate, mostly scarious-margined and the sinuses commonly scarious. Corolla salver-form, the tube narrow, the limb 5-lobed; lobes obovate, orbicular or obcordate, spreading. Stamens straight, short, unequally inserted on the corolla-tube, included. Ovary oblong or ovoid, 3-celled; style usually slender; ovules 1-4 in each cavity. Capsule ovoid, 3-valved, at length distending and rupturing the calyx-tube. Seeds usually only 1 in each cavity of the capsule, ovoid, wingless or narrowly winged, not emitting spiral threads when wetted. [Greek, flame.]
About 40 species, natives of North America and Russian Asia, many of them widely cultivated. Besides the following, some 24 others occur in the southern and western parts of North America. Type species: Phlox glaberrima L. Leaves flat, ovate, oblong, lanceolate or linear.
Cymes panicled; flowers short-pedicelled or sessile. Calyx-teeth subulate.
Stem glabrous or puberulent: leaves lanceolate to oblong.
1. P. paniculata.
Stem villous, glandular above: leaves ovate to ovate-lanceolate.
2. P. amplifolia.
Calyx-teeth lanceolate, acute; leaves lanceolate or ovate, acuminate.
3. P. maculata.
Cymes corymbose, simple, or flowers scattered. Flowering stems erect or ascending, simple. Plants glabrous or nearly so.
Leaves ovate or oblong; calyx-teeth acute.
4. P. ovata.
Leaves lanceolate or linear; calyx-teeth subulate-lanceolate.
5. P. glaberima.
Plants pubescent, hirsute or villous.
Stems erect or ascending; no prostrate sterile shoots. Leaves linear or lanceolate, acuminate, spreading.
6. P. pilosa.
Leaves linear-oblong, acute or obtuse, nearly erect.
7. P. amoena.
Stems ascending or reclining; sterile shoots prostrate.
Lower leaves and those of the sterile shoots oblong or ovate.
8. P. divaricata.
Lower leaves and those of the sterile shoots obovate.
9. P. stolonifera.
Stems diffusely branched, usually creeping; leaves narrow. Corolla-lobes cleft to or about the middle.
10. P. bifida.
Corolla-lobes cleft only at the apex.
11. P. Stellaria.
Corolla-lobes rounded: western.
12. P.Kelseyi, Leaves subulate, fascicled or crowded; plants low.
Stems creeping or ascending; flowers cymose; eastern. Corolla-lobes shallowly emarginate; plant not glandular.
Corolla-lobes deeply emarginate; upper part of plant glandular.
14. P. Brittonii.
Densely tufted; flowers mostly solitary; western.
Leaves densely white-woolly, 1" long; plant moss-like.
15. P. bryoides.
Leaves less woolly or merely ciliate, 2 -6' long. Corolla-tube shorter than or equalling the calyx.
16. P. Hoodii.
Corolla-tube longer than the calyx.