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Peridiscaceae is a family of flowering plants in the order Saxifragales.〔Peter F. Stevens. 2001 onwards. "Peridiscaceae". At: Angiosperm Phylogeny Website At: Missouri Botanical Garden Website. (see ''External links'' below).〕 It comprises four genera: ''Medusandra, Soyauxia, Peridiscus'', and ''Whittonia''.〔Kenneth J. Wurdack and Charles C. Davis. 2009. "Malpighiales phylogenetics: Gaining ground on one of the most recalcitrant clades in the angiosperm tree of life." ''American Journal of Botany'' 96(8):1551-1570.〕 It has a disjunct distribution, with ''Peridiscus'' occurring in Venezuela and northern Brazil, ''Whittonia'' in Guyana,〔Clemens Bayer. 2007. "Peridiscaceae" pages 297-300. In: Klaus Kubitski (editor). ''The Families and Genera of Vascular Plants'' volume IX. Springer-Verlag: Berlin;Heidelberg, Germany. ISBN 978-3-540-32214-6〕 ''Medusandra'' in Cameroon, and ''Soyauxia'' in tropical West Africa.〔Vernon H. Heywood, Richard K. Brummitt, Ole Seberg, and Alastair Culham. ''Flowering Plant Families of the World''. Firefly Books: Ontario, Canada. (2007). ISBN 1-55407-206-9〕 ''Whittonia'' is possibly extinct, being known from only one specimen collected below Kaieteur Falls in Guyana. An attempt to rediscover it in 2006 was not successful.〔 The largest genus is ''Soyauxia'', with about seven species. ''Medusandra'' has two species. ''Peridiscus'' and ''Whittonia'' each contain one species. The Peridiscaceae are small trees or erect shrubs of wet tropical forests. It was not until 2009 that all four of the genera were united into a single family.〔 ''Peridiscus'' and ''Whittonia'' are clearly close relatives. This pair, and the other two genera have long been considered anomalous, being variously classified by different authors. == Description == The following description was created by combining descriptions of ''Medusandra'' and ''Peridiscus'' by John Hutchinson 〔John Hutchinson. ''The Families of Flowering Plants, Third Edition (1973)''. Oxford University Press: London.〕 with descriptions of ''Soyauxia'', ''Peridiscus'', and ''Whittonia'' by Clemens Bayer.〔 Peridiscaceae are small trees or erect shrubs. The leaves are stipulate, alternate, and simple, with margins that are entire or remotely crenulate (''Medusandra''). The petiole is pulvinate, at its apex, sometimes obscurely so. The stipules are in the axils of the leaves, sometimes enclosing an axillary bud. The inflorescence is a cluster of axillary racemes or spikes, the clusters often being reduced to a pair of racemes or to a single raceme. The flowers are bisexual and actinomorphic. The sepals are 4 to 7 in number, and free, that is, separate from each other. ''Medusandra'' and ''Soyauxia'' have five petals. ''Peridiscus'' and ''Whittonia'' have none. ''Medusandra'' lacks a nectary disk and has five stamens, inserted opposite the petals, and alternating with five long, hairy staminodes. In the others, the stamens are numerous and arranged in a ring around the nectary disk. The anthers are tetrathecal in ''Medusandra'' and ''Soyauxia''; bithecal in ''Peridiscus'' and ''Whittonia''. The perianth parts are attached below the ovary. The ovary is therefore superior, but appears half-inferior in ''Peridiscus'' because the ovary is embedded in the large, fleshy disk. The gynoecium consists of three or four carpels, united to form a unilocular ovary. The placentation is apical, with two ovules at the apex of each carpel. The ovary has a central column in ''Medusandra'' and ''Soyauxia''. Each carpel bears a stylulus and these are well separated at the apex of the ovary. The fruit is one-seeded; a capsule in ''Medusandra'' and ''Soyauxia''; a drupe in ''Peridiscus'' and ''Whittonia''. 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「Peridiscaceae」の詳細全文を読む スポンサード リンク
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