RHAMNACEAE, buckthorn family
Plants shrubs,
trees, or lianas, sometimes dioecious (sometimes incompletely so), sometimes
the branchlets thorny at the tip. Leaves alternate or opposite. Stipules absent
or more commonly present, but minute, scalelike, and shed early (spinescent
elsewhere). Leaf blades simple, unlobed, the venation with 3 main veins from
the base or with 1 midvein and pinnate secondary veins, these sometimes
strongly arched toward the blade tip. Inflorescences terminal or axillary
clusters, umbels, or panicles, sometimes reduced to solitary flowers, the
branch points or flowers sometimes subtended by small bracts, but these usually
shed early. Flowers relatively small, actinomorphic, perfect or imperfect,
shallowly perigynous, the hypanthium variously saucer-shaped to somewhat
cup-shaped, usually persistent and becoming disc-shaped, even after the fruits
have been shed. Calyces of 4 or 5 apparently free sepals, these attached to the
hypanthium rim (and thus can be interpreted as fused into the hypanthium
basally), usually not persistent above the hypanthium at fruiting. Corollas of
4 or 5 free petals, these often tapered to a stalklike base, white or whitish
green. Stamens 4 or 5, positioned opposite the petals, the filaments usually
distinct, attached at the petal bases and often partially enclosed by the
concave petals, reduced or absent in pistillate flowers, the anthers attached
near the midpoint or at the base, usually yellow. Nectar disc present between
the stamens and pistil, more or less cushion-shaped. Pistil of 2 or 3(4) fused
carpels, reduced or absent in staminate flowers. Ovary superior, 2- or
3(4)-locular, the locules sometimes incomplete toward the ovary tip, the
placentation more or less axile (often appearing nearly basal), the ovules 1
per locule. Style 1 and entire or 2–4-branched, the stigmas variously 2- or
3-lobed or entire, more or less capitate. Fruits drupes or appearing capsular
(schizocarps or samaras elsewhere), indehiscent or more or less dehiscent, the
stones 1–4, bony. About 55 genera, about 950 species, nearly worldwide, most
diverse in tropical and warm-temperate regions.
The main use of
members of the Rhamnaceae in the United States is as ornamental plants in
gardens. However, some of the genera contain medicinally important species
(particularly as laxatives). Some of the tropical genera provide lumber for
buildings and furniture, as well as handcrafts and musical instruments. Species
of jujube are members of the genus Ziziphus Mill., some of which are
cultivated for their edible fruits