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..
A fringed crown in the throat of the calyx; our species vines; stamens 5; ovary free from the calyx. Fam. 91. Passifloraceae. 2:564.
No crown; our species herbs; stamens numerous; ovary adnate to the calyx.
Fam. 92. Loasaceae. 2: 565.
II. Ovary inferior, adnate to the calyx, wholly, or in part (except in Lythraceae and our Melasto-maceae, where it is usually merely enclosed by it, and in Thymeleaceae and Elaeagnaceae, which are shrubs or trees, with no corolla).
Order 21. Opuntiales. One family.
Fam. 93. Cactaceae. 2: 568.
2. Herbs, shrubs or trees, not fleshy nor spiny; calyx-segments and petals (when present) rarely more than 5. Petals none in our species; shrubs or trees; ovary i-ovuled. Order 22. Thymeleales.
Leaves green; seed pendulous. Fam. 94. Thymeleaceae. 2: 574.
Leaves silvery-scurfy; seed erect. Fam. 95. Elaeagnaceae. 2:575.
Petals present (except in some Haloragidaceae, which are small aquatic herbs).
Ovules several or numerous in each cavity of the ovary (except in Haloragidaceae and Trap-aceae). • Order 23. Myrtales (Myrtiflorae).
Land or marsh plants, or, if aquatic, submerged leaves not dissected.
Calyx-tube merely enclosing the ovary, but free from it (except at the base).
Anthers longitudinally dehiscent. Fam. 96. Lythraceae. 2: 577.
Anthers opening by a terminal pore. Fam. 97. Melastomaceae. 2: 582.
Calyx-tube almost wholly adnate to the ovary. Fam. 98. Onagraceae. 2: 584.
Aquatic or amphibious herbs, the submerged leaves dissected (except in Hippuris, which has whorled narrow leaves and only 1 stamen.
Fam. 99. Trapaceae. 2:611.
Leaves most sessile; petioles, if present, not inflated; flowers small, greenish; seeds with 1 coat. Fam. 100. Haloragidaceae. 2:612.
Ovules 1 in each cavity of the ovary. Order 24. Umbellales (Umbelliflorae).
Stamens 5; styles 2-5, rarely united; flowers umbellate or capitate.
Fruit a fleshy berry or drupe. Fam. 101. Araliaceae. 2: 616.
Fruit dry when mature, splitting into two mericarps. Fam. 102. Ammiaceae. 2: 619.
Stamens 4; style 1; stigma 1; shrubs and trees; flowers not umbellate.
Fam. 103. Cornaceae. 2:660.
Series 2. Gamopetalae.
2: 666 to 3: 560. Petals more of less united. (See exceptions noted on page 666, Vol. 2.)
A. Ovary superior (except in Vacciniaceae and Symplocaceae, in which it is partly or wholly inferior).
I. Stamens mostly free from the corolla, or adnate merely to its base (at the sinuses of the corolla in Diapensia and Pyxidanthera of the Diapensiaceae), as many as the lobes and alternate with them, or twice as many. Order 1. Ericales.
Stamens free from the corolla, or merely adnate to its base, not united into a tube. Ovary superior; fruit a capsule, or rarely drupaceous. Corolla essentially polypetalous.
Ovary 3-celled; shrubs; leaves deciduous. Fam. 1. Clethraceae. 2:666.
Ovary 4-5-celled; low, mostly evergreen perennials. Fam. 2. Pyrolaceae. 2: 667.
Corolla distinctly gamopetalous (except in Monotropa and Hypopitys of the Monotropaceae and Ledum of the Ericaceae■).
Herbaceous saprophytes without green leaves. Fam. 3. Monotropaceae. 2: 673.
Shrubs with normal, often evergreen leaves. Fam. 4. Ericaceae. 2:675.
Ovary inferior, adnate to the calyx, forming a many-seeded berry in fruit.
Fam. 5. Vacciniaceae. 2:694.
Stamens borne at the sinuses of the corolla, or united in a io-lobed tube.
Fam. 6. Diapensiaceae. 2: 705.
II. Stamens borne on the corolla, as many as its lobes and opposite them, or twice as many, or more. Herbs. • Order 2. Primulales.
Style 1; fruit a capsule. Fam. 7. Primulaceae. 2: 707.
Styles 5; fruit an achene or utricle. Fam. 8. Plumbaginaceae. 2: 717,
Shrubs or trees. Order 3. Ebenales.
Stamens as many as the corolla-lobes. Fam. 9. Sapotaceae. 2: 719. Stamens twice as many as the corolla-lobes, or more.
Styles 2-8; flowers mostly monoecious or dioecious. Fam. 10. Ebenaceae. 2: 720. Style 1, simple or lobed; flowers mostly perfect.
Stamens in several series. Fam. 11. Symplocaceae. 2: 711.
Stamens in 1 series. Fam. 12. Styracaceae. 2: 711.
III. Stamens borne on the corolla, as many as its lobes or fewer, and alternate with them (in our species of Fraxinus and Forestiera of the Oleaceae there is no corolla).
* Corolla not scarious, nerved.
t Ovaries 2, distinct (except in some Loganiaceae, and in Gentianaceae and Menyanthaceae, in which the ovary is compound, with 2 cavities, or rarely more, or with 1 cavity and 2 placentae); flowers regular; stamens mostly adnate to only the lower part of the corolla; leaves mostly opposite.
Order 4. Gentianales (Contortae).
a. Stamens (usually 2), fewer than the corolla-lobes, or corolla none; our species trees or shrubs.
Fam. 13. Oleaceae. 2: 723. b. Stamens as many as the corolla-lobes; mostly herbs. Stigmas distinct; juice not milky; ovary 1, compound.
Ovary 2-celled; leaves stipulate, or their bases connected by a stipular line.
Fam. 14. Loganiaceae. 2: 729. Ovary i-celled; leaves not stipulate.
Leaves opposite or rarely verticillate; corolla-lobes convolute or imbricated in the bud.
Fam. 15. Gentianaceae. 3:1. Leaves basal or alternate; corolla-lobes induplicate-valvate in the bud; marsh or aquatic herbs. Fam. 16. Menyanthaceae. 3:17.
Stigmas united; juice milky; ovaries 2 in our species.
Styles united; stamens distinct; pollen of simple grains. Fam. 17. Apocynaceae. 3: 19.
Styles distinct; stamens mostly monadelphous; pollen-grains united into waxy masses.
Fam. 18. Asclepiadaceae. 3:23.