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The Platanaceae are a family of flowering plants belonging to the order Proteales. This family has been recognized by almost all taxonomists, and is sometimes called the "plane-tree family". The family consists of only a single extant genus ''Platanus'', with seven accepted species of the more than 40 described. The plants are tall trees, native to temperate and subtropical regions of the Northern Hemisphere. The hybrid London plane is widely planted in cities worldwide. The plane-tree is referenced in Pliny the Younger's letter to Domitius Apollinaris as part of his description of his Tuscan Villa located somewhere in Tuscany in the first century. == Description == * Large, sympodial, deciduous tree, speckled bark that sheds in large irregular sheets, leaving a smooth surface that is mottled and pale, persistent bark at the base of the trunk, indumentum with large glandular hairs, multicellular and uniserrate or short with uniserrate ramification (in candelabrum), in stellate fascicles; glandular hairs with unicellular, globular capitulum, cuticular waxes without crystalloids, with rods and plates * Leaves generally with very variable shapes and nervation, simple, alternate, more or less distichous, isobilateral palmate with three to seven lobes (palmatifid to palmatisect) with whole edges or with glandular teeth (each one with a midvein that broadens towards the glandular apex, where it ends in an open hole), or penninerved and whole (''Platanus kerrii''), this shape common in young, vernal leaves in other species, vernation folded, with the petiole usually sheathed, enclosing the axillary bud (bud is free in ''P. kerrii''), stipules foliose, large, intrapetiolar, tubular, normally caduceus, in ''P. kerrii'' scarious, small, basally fused to the petiole, domatia present, stomata irregularly anomocytic * Stems with aggregated rays in the xylem, with nodes septilacunar, cork cambium present and superficial, buds covered by single scale * Plants monoecious, the flowers of each sex in separate inflorescences * Inflorescences in large hanging peduncles, each one a unisexual, globular capitellum, pedunclulate or seated, with numerous flowers, derived from the condensation of a panicle, with a circular bract at the base and bracteoles among the flowers * Flowers small, inconspicuous, hypogenous, regular unisexual, receptacle short, smooth, hypogynous disk absent, perianth reduced, sepals number three to four, rarely eight, free or basally fused, shorter than the petals, triangular. Petals number three to four, rarely eight, truncated-spatulate or vestigial, scarious, frequently absent in the female flowers, male flowers with androecium haplostemonous, isostemonous, oppositisepal, with number three to four, rarely eight, stamens, gynostemium short or vestigial, anthers basifixed, not versatile, dithecous, tetrasporangiate, elongated, connectivum apically widened, peltate, dehiscence along longitudinal valves; pistillidium sometimes present, female flowers with superior gynoecium carpels apocarpous in two or three whorls, imperfectly closed apically, surrounded by large petals, linear stylodious, stigmas internal, decurrent in two ridges, more or less dry, two ovules per carpel but one nearly always aborts, orthotropous, bitegmic, crassinucellated, pendulous, apical to marginal placentation, three or four staminodes 3-4, no nectaries * Fruits in achene, clavate, grouped in a globular capituliform infructescence, each fruit surrounded by long hairs Image:Platanus orientalis fruit body 01.jpg|Fruiting body of ''P. orientalis'' (Oriental plane tree). Image:American sycamore (Platanus occidentalis) 2.jpg|Fruiting body of American sycamore (''P. occidentalis'') with some achenes removed Image:Platanus nucula 01.JPG|An achene Image:Fruit morphology fruit type - achene (from multiple fruit of achenes Platanus).svg|Cross section of an achene with the seed shown in brown * Seeds small with thin testa with little endosperm, oily and proteinaceous, embryo thin and straight with two linear cotyledons, often uneven * Pollen in subprolate monads, 16-22 μm in length, tricolpate, sometimes sextarugate, tectate-columellate, reticulated surface, the base layer as thick as the tectum * Chromosomal number: ''2n'' = 14, 16, 21, 42; ''x'' probably equal to 7 or 8 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「Platanaceae」の詳細全文を読む スポンサード リンク
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