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, shrubs, vines, or some tropical species trees, with alternate or rarely opposite, exstipulate entire dentate lobed or dissected leaves, and perfect regular or nearly regular cymose flowers. Calyx inferior, gamosepalous, mostly 5-lobed. Corolla gamopetalous, rotate, campanulate, funnelform, salverform or tubular, mostly 5-lobed, the lobes induplicate-valvate or plicate in the bud. Stamens as many as the lobes of the corolla and alternate with them, inserted on the tube, all equal and perfect in the following genera, except in Petunia, where 5 are didynamous and the fifth smaller or obsolete; anthers 2-celled, apically or longitudinally dehiscent. Disk present, or none. Ovary entire, superior, 2-celled (rarely 3-5-celled); ovules numerous on the axile placentae, anatropous or amphitropous; style slender, simple; stigma terminal; fruit a berry or capsule. Seeds numerous, the testa sometimes roughened; embryo terete, spiral, curved, or nearly straight; endosperm fleshy; cotyledons semiterete.
About 75 genera and 1750 species, widely distributed, most abundant in tropical regions. * Fruit a pulpy berry; corolla plicate, its lobes generally induplicate. Anthers unconnected, destitute of terminal pores, dehiscent. Fruiting calyx bladdery-inflated.
Fruiting calyx 5-angled and deeply 5-parted; ovary 3-5-celled.
Fruiting calyx 5-lobed, not parted, 10-ribbed, often 5-10-angled, reticulated, wholly enclosing the berry; ovary 2-celled. Corolla open-campanulate, yellowish or whitish, often with a dark center; seeds with a thin margin, finely pitted.
Fruiting calyx somewhat enlarged, but closely fitted to the fruit, thin, obscurely veiny, open at the mouth. Corolla rotate, whitish; lobes of fruiting calyx much exceeding the berry.
Corolla rotate, whitish, sometimes tinged with purple; fruiting calyx not exceeding the berry. Anthers connivent or slightly connate; fruiting calyx not enlarged.
Anthers short or oblong, opening by a terminal pore or short slit in our species.
Anthers long, tapering from base to summit, longitudinally dehiscent.
** Fruit a nearly dry berry; corolla campanulate, little or not at all plicate, its lobes imbricated.
*** Fruit a capsule; corolla funnelform. Capsule circumscissile toward the top, which separates as a lid; corolla irregular.
Capsule opening by valves. Capsule generally prickly.
Capsule not prickly.
Flowers paniculate or racemose; stamens nearly uniform in length.
Flowers solitary; stamens very unequal.