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Roystonea
''Roystonea'' is a genus of eleven species of monoecious palms, native to the Caribbean Islands, and the adjacent coasts of Florida and Central and northern South America.〔(Kew World Checklist of Selected Plant Families )〕〔(Flora of North America, ''Roystonea'' O. F. Cook, Science. ser. 2, 12:479. 1900. )〕〔Govaerts, R. & Dransfield, J. (2005). World Checklist of Palms: 1-223. The Board of Trustees of the Royal Botanic Gardens, Kew. 〕 Commonly known as the royal palms, the genus was named for Roy Stone, a U.S. Army engineer. It contains some of the most recognizable and commonly cultivated palms in tropical and subtropical regions.
==Description==
''Roystonea'' is a genus of large, unarmed, single-stemmed palms with pinnate leaves. The large stature and striking appearance of a ''Roystonea'' palm makes it a notable aspect of the landscape. The stems, which were compared to stone columns by Louis and Elizabeth Agassiz in 1868, are smooth and columnar, although the trunks of ''R. altissima'' and ''R. maisiana'' are more slender than those of typical royal palms. Stems often are swollen and bulging along portions of their length, which may reflect years where growing conditions were better or worse than average. Leaf scars are often prominent along the stem, especially in young, rapidly growing individuals. Stem color ranges from gray-white to gray-brown except in ''R. violacea'', which have violet-brown or mauve stems. The largest royal palm, ''R. oleracea'', reaches heights of , but most species are in the range.
''Roystonea'' leaves consist of a sheathing leaf base, a petiole, and a rachis. The leaf base forms a distinctive green sheath around the uppermost portion of the trunk. Known as the crownshaft, this sheath extends down the trunk. The petiole connects the lead base with the rachis. Zona only reported petiole lengths for three of the 10 species, ranging from . The rachis is pinnately divided and ranges from long. The leaf segments themselves range in length from in ''R. altissima'' up to as much as in ''R. lenis''. They are arranged in two or three planes along the rachis. Many authors have reported that the leaves ''R. oleracea'' are arranged in a single plane, but American botanist Scott Zona reported that this is not the case.〔
These plants have the ability to easily release their leaves in strong winds, a supposed adaption serving to prevent toppling during hurricanes. Inflorescences occur beneath the crownshaft, emerging from a narrow, horn-shaped bract. The flowers on the branched panicles are usually white, unisexual, and contain both sexes. The fruit is an oblong or globose drupe long and deep purple when ripe. Some species so closely resemble one another that scientific differentiation is by inflorescence detail; flower size, colour, etc.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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