This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol1", 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..
tt Ovary 1, compound (2-divided in Dichondra; in Boraginaceae and Labiatae mostly deeply 4-lobed around the style) flowers regular or irregular; stamens mostly adnate to the middle of the corolla-tube or beyond; leaves opposite or alternate.
Order 5. Polemoniales (Tubiflorae).
a. Corolla regular (irregular in Echium of the Boraginaceae).
Ovary not 4-lobed, the carpels not separating as separate nutlets at maturity.
Ovary 2-divided. Fam. 19. Dichondraceae. 3: 39.
Ovary 2-celled, rarely 3-4-celled; style 1, entire, 2-cleft, or 2-parted; mostly twining vines. Leaves normal. Fam. 20. Colvolvulaceae. 3: 40.
White or yellowish parasitic vines, the leaves reduced to minute scales.
Fam. 21. Cuscutaceae. 3:48. Ovary 3-celled; stigmas 3, linear; herbs, not twining. Fam. 22 Polemoniaceae. 3: 52.
Ovary i-celled (2-celled in Nama); style 1, 2-lobed, or 2-parted; herbs, not twining.
Fam. 23. Hydrophyllaceae. 3: 65. Ovary deeply 4-lobed around the style, or not lobed (Heliotropium); carpels separating as nutlets.
Fam. 24. Boraginaceae. 3: 72.
b. Corolla irregular, more or less 2-lipped (regular in Solanaceae, in Mentha and Lycopus of the Labiatae, and nearly or quite so in Verbena and Callicarpa of the Verbenaceae).
1. Carpels 1-2-seeded.
Ovary not lobed, 2-4-celled, the style apical; carpels separating into i-seeded nutlets.
Fam. 25. Verbenaceae. 3:94. Ovary 4-lobed around the style, the lobes ripening into i-seeded nutlets. Fam. 26. Labiatae. 3: 99.
2. Carpels several-many-seeded (2-seeded in some Acanthaceae).
| Fruit a berry, or more commonly * capsule which is 1-2-celled, 2-valved, circumscissile, or irregularly bursting, not elastically dehiscent.
Ovary 2-celled, or rarely 3-5-celled.
Flowers regular; fertile stamens 5 (4 in Petunia); fruit a berry or capsule.
Fam. 27. Solanaceae. 3: 154. Flowers more or less irregular; fertile stamens 2 or 4 (5 in Verbascum); fruit a capsule.
Fam. 28. Scrophulariaceae. 3:172. Ovary 1-celled; marsh or aquatic herbs with flowers on scapes.
Fam. 29. Lentibulariaceae. 3: 225. Placentae parietal.
Herbs, parasitic on the roots of other plants, the leaves reduced to scales, not green; ovary i-celled. Fam. 30. Orobanchaceae. 3:233.
Trees, vines, shrubs, or herbs, the foliage normal.
Trees, shrubs, or woody vines; capsule 2-celled; seeds winged in our genera.
Fam. 31. Bignoniaceae. 3:236.
Opposite-leaved herbs; capsule i-celled in our genus; seeds wingless.
Fam. 32. Martyniaceae. 3: 239.
Jt Capsule completely 2-celled, elastically loculicidally dehiscent; opposite-leaved herbs; placentae axile.
Fam. 33. Acanthaceae. 3: 239. 3. Ovary and fruit i-celled with 1 erect orthotropous ovule and seed; herb with spicate flowers and reflexed fruits.
Fam. 34. Phrymaceae. 3: 244. ** Corolla scarious, nerveless.
Order 6. Plantaginales. Herbs with small spicate or capitate flowers; one family. Fam. 35. Plantaginaceae. 3: 245.
B. Ovary inferior.
I. Anthers distinct.
Stamens as many as the corolla-lobes and alternate with them (one fewer in Linnaea of the Capri-foliaceae), or twice as many; ovary compound, with 1 ovule or more in each cavity; leaves opposite, or verticillate. Order 7. Rubiales.
Stamens as many as the corolla-lobes.
Leaves always stipulate, usually blackening in drying. Fam. 36. Rubiaceae. 3: 250.
Leaves usually exstipulate, not blackening in drying. Fam. 37. Caprifoliaceae. 3: 267.
Stamens twice as many as the corolla-lobes; low herb with ternately divided leaves.
Fam. 38. Adoxaceae. 3:283.
Stamens mostly fewer than the corolla-lobes; ovary 1-celled with 1 pendulous ovule, or 3-celled with 2 of the cavities without ovules. Order 8. Valerianales (Aggregatae).
Ovary 3-celled, 2 of its cavities empty. Fam. 39. Valerianaceae. 3: 284.
Ovary i-celled; flowers densely capitate, involucrate. Fam. 40. Dipsacaceae. 3:288.
II. Anthers united (except in Campanula and Specularia of the Campanulaceae, in Ambrosiaceae, and in Kuhnia of the compositae). Order 9. Campanulales (Campanulatae).
Flowers not in involucrate heads; juice mostly milky.
Endosperm none; flowers monoecious or dioecious; our species vines.
Fam. 41. Cucurbitaceae. 3:290. Endosperm present, fleshy; flowers perfect.
Flowers regular. Fam..42. Campanulaceae. 3:293.
Flowers irregular. Fam. 43. Lobeliaceae. 3: 299.
Flowers in involucrate heads.
Flowers all expanded into rays (ligulate); juice milky. Fam. 44. Cichoriaceae. 3: 304.
Flowers all tubular, or the outer expanded into rays; juice very rarely milky.
Stamens distinct, or nearly so. Fam. 45. Ambrosiaceae. 3: 338.
Stamens united by their anthers into a tube around the style (except in Kuhnia).
Fam. 46. Compositae. 3: 347.