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''Rhamnaceae'' is a large family of flowering plants, mostly trees, shrubs, and some vines, commonly called the buckthorn family.〔 The family contains 50–60 genera and approximately 870–900 species. Rhamnaceae have a worldwide distribution, but are more common in the subtropical and tropical regions. The earliest fossil evidence of Rhamnaceae is from the Eocene. Leaves of Rhamnaceae family members are simple, i.e., the leaf blades are not divided into smaller leaflets.〔Flowering Plants of the Santa Monica Mountains, Nancy Dale, 2nd Ed. 2000, p. 166〕 Leaves can be either alternate and spiraling, or opposite. Stipules are present. These leaves are modified into spines in many genera, in some (e.g. ''Paliurus spina-christi'' and ''Colletia cruciata'') spectacularly so. ''Colletia'' stands out by having two axillary buds instead of one, one developing into a thorn, the other one into a shoot. The flowers are radially symmetrical. There are 5 (sometimes 4) separate sepals and 5 (sometimes 4 or none) separate petals. The petals may be white, yellowish, greenish, pink or blue, and are small and inconspicuous in most genera, though in some (e.g. ''Ceanothus'') the dense clusters of flowers are conspicuous. The 5 or 4 stamens are opposite the petals.〔 The ovary is superior, with 2 or 3 ovules (or one by abortion). The fruits are mostly berries, fleshy drupes or nuts. Some are adapted to wind carriage, but most are dispersed by mammals and birds. Chinese jujube is the fruit of the jujube tree (''Ziziphus zizyphus'') and is a major fruit in China. The American genus ''Ceanothus'', which has several showy ornamental species, has nitrogen-fixing root nodules. Economic uses of Rhamnaceae are chiefly as ornamental plants and as the source of many brilliant green and yellow dyes. The wood of ''Rhamnus'' was also the most favoured species to make charcoal for use in gunpowder before the development of modern propellants. == Genera == 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Rhamnaceae」の詳細全文を読む スポンサード リンク
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