Rosidae: Rhamnales. The Rhamnaceae are mainly trees or shrubs, sometimes twining or climbing, comprising about 55 genera and 900 species. The leaves are simple, mostly alternate, and usually stipulate. The flowers are actinomorphic, commonly small and greenish, and nearly always bisexual. The calyx is generally 5-lobed, typically arising from a perigynous or rarely an epigynous zone. The corolla consists typically of 5 clawed, distinct petals or rarely is absent. The androecium comprises typically 5 stamens that are opposite and commonly embraced by the petals. The gynoecium consists of a single compound pistil of usually 2-4 carpels, a lobed or cleft style, and a superior or rarely inferior ovary with usually 2-4 locules, each with almost always a single basal ovule. An annular nectary disk surrounds and is usually adnate to the ovary. The fruit is usually drupaceous.
Each "thumbnail" image below is linked to a larger photograph.
 |
Gouania hillebrandii. The perianth scars on the summit of the epigynous zone of the fruit of this Hawaiian endemic clearly reveals that it has an inferior ovary, making it one of the rare exceptions in the family. Note the whitish nectary disk in which the ovary is embedded, and the small petals cupped around the opposite stamens. | ||
|
Colubrina oppositifolia, kauila. This endemic Hawaiian species was valued for its hard, durable wood. A developing fruit is on the right. In the lower, enlarged view of the flower note the small greenish petals embracing the whitish stamens, and the very conspicuous nectary disk surrounding the pistil. | ||
 |
Alphitonia ponderosa, kauila. Small, cup-like petals opposite the stamens and a conspicuous yellowish nectary disk characterize this Hawaiian endemic. | ||
 |
Rhamnella vitiense. Note the small greenish flowers and the whitish hood-like petals opposite the stamens. | ||
 |
Ceanothus sp., buckthorn. The long-clawed petals are spreading in this example. The sepals are petaloid, and the nectary disk is blackish. |
