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 or some tropical genera trees, with opposite verticillate or rarely alternate leaves, and perfect, more or less irregular, or sometimes regular flowers, in terminal or axillary spikes, racemes, cymes or panicles. Calyx inferior, mostly persistent, usually 4-5-lobed or 4-5-cleft. Corolla gamopetalous, regular, or 2- lipped, the tube usually cylindric and the limb 4-5-cleft. Stamens 4, didy-namous, rarely only 2, or as many as the corolla-lobes, inserted on the corolla and alternate with its lobes; anthers 2-celled, the sacs longitudinally dehiscent. Ovary superior, 2-4-celled (rarely 8-10-celled), composed of 2 carpels, each carpel with 2 anatropous or amphitropous ovules, thus in 4-celled ovaries 1 ovule in each cavity; style terminal, simple; stigmas 1 or 2. Fruit dry, separating at maturity into 2-4 nutlets, or a drupe containing the 2-4 nutlets. Endosperm little or none, or rarely fleshy; embryo straight.
About 75 genera and 1300 species, of wide geographic distribution in temperate and warm regions.
Flowers in heads or spikes; ovary 2-4-celled; fruit of 2 or 4 erect nutlets; ours herbs. Corolla-limb 5-lobed. regular or nearly so: nutlets 4.
Corolla-limb 4-lobed, 2-lipped; nutlets 2.
Flowers in axillary cymes; shrubs; fruit drupaceous.