This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol2", 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..
[?Oenoplea Hedw. f. Gen. 1: 151. 1806.]
Climbing or erect shrubs, with alternate petioled ovate or oblong coriaceous pinnately-veined leaves, and small greenish-white flowers in axillary or terminal clusters, or rarely solitary. Calyx-tube hemispheric, the limb 5-toothed. Petals 5, sessile, concave or cucullate. Stamens 5; filaments filiform. Disk filling the calyx-tube, covering but not united with the ovary. Drupe oval, obtuse, compressed, its flesh thin and coriaceous, its stone 2-celled. Seeds linear-oblong; cotyledons thin. [Name unexplained.]
About 10 species, the following typical one in southeastern North America, the others in Asia and tropical Africa.
A glabrous high-climbing shrub, with slender tough terete branches. Leaves ovate or ovate-oblong, 1'-2' long, 1/2 - 1' wide, acute, acuminate, or obtuse and cuspidate at the apex, obtuse or somewhat truncate at the base, dark green above, paler beneath, their margins undulate and sometimes slightly revolute; veins 8-12 pairs; petioles slender, 2"-5" long; flowers about 1 1/2" broad, mainly in small terminal panicles; petals acute; style short; drupe 3"-4" long, equalling or shorter than its slender pedicel, its stone crustaceous.
2. RHÁMNUS [Tourn.] L. Sp. Pl. 193. 1753.
Shrubs or small trees, with alternate pinnately veined and (in our species) deciduous leaves, and small axillary cymose, racemose or paniculate, perfect, dioecious, or polygamous flowers. Calyx-tube urceolate, its limb 4-5-toothed. Petals 4-5, short-clawed, mainly emar-ginate and hooded, or none. Disk free from the 3-4-celled ovary. Style 3-4-cleft. Drupe berry-like, oblong or globose, containing 2-4 separate nutlet-like stones. Seeds mainly obovoid; endosperm fleshy; cotyledons flat or revolute. [The ancient Greek name.]
About 90 species, natives of temperate and warm regions. Besides the following, some 10 others occur in the western United States and British America. Type species: Rhamnus cathartica L.
Flowers dioecious or polygamous; nutlets grooved.
Petals present; flowers mainly 4-merous.
Leaves broadly ovate; branches thorny; drupe with 3 or 4 nutlets.
Leaves ovate-lanceolate; drupe with 2 nutlets.
Petals none; flowers 5-merous; drupe with 3 nutlets.
Flowers perfect; nutlets smooth.
Umbels peduncled; leaves acute; calyx campanulate.
Umbels sessile; leaves obtuse; calyx hemispheric.