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''Thuja'' ( )〔''Sunset Western Garden Book,'' 1995:606–607 〕 is a genus of coniferous trees in the Cupressaceae (cypress family). There are five species in the genus, two native to North America and three native to eastern Asia.〔(Kew World Checklist of Selected Plant Families )〕〔Farjon, A. (2005). ''Monograph of Cupressaceae and Sciadopitys''. Royal Botanic Gardens, Kew. ISBN 1-84246-068-4〕〔Gymnosperm Database: (''Thuja'' )〕〔(Flora of North America Vol. 2 Arborvitae, thuya, cèdre, ''Thuja'' Linnaeus, Sp. Pl. 2: 1002. 1753; Gen. Pl. ed. 5, 435, 1754. )〕〔(Flora of China Vol. 4 Page 63 崖柏属 ya bai shu ''Thuja'' Linnaeus, Sp. Pl. 2: 1002. 1753. )〕 The genus is monophyletic and sister to ''Thujopsis''. They are commonly known as arborvitaes (from Latin for ''tree of life'') or thujas; several species are widely known as ''cedar'' but because they are not true cedars (''Cedrus'') it has been recommended to call them redcedars or whitecedars.〔Kelsey, H. P., & Dayton, W. A. (1942). ''Standardized Plant Names'', second edition. American Joint Committee on Horticultural Nomenclature. Horace McFarland Company, Harrisburg, Pa.〕 ;Species〔〔(Biota of North America Program 2013 county distribution maps )〕 # ''Thuja koraiensis'' Nakai - Korean Thuja - Jilin, Korea # ''Thuja occidentalis'' L. - Eastern Arborvitae, Northern Whitecedar - E Canada (Manitoba to Nova Scotia), E USA (primarily Northeast, Great Lakes, Appalachians) # ''Thuja plicata'' Donn ex D.Don - Western Redcedar - from Alaska to Mendocino County in California # ''Thuja standishii'' (Gordon) Carrière - Japanese Thuja - Honshu, Shikoku # ''Thuja sutchuenensis'' (Gordon) Carrière - Sichuan Thuja - Sichuan, Chongqing China almost extinct in the wild ;Formerly placed here〔 * ''Austrocedrus chilensis'' (D.Don) Pic.Serm. & Bizzarri (as ''T. chilensis'' D.Don) * ''Callitris rhomboidea'' R.Br. ex Rich. (as ''T. australis'' Poir.) * ''Cupressus nootkatensis'' D.Don (as ''T. excelsa'' Bong.) * ''Glyptostrobus pensilis'' (Staunton ex D.Don) K.Koch (as ''T. pensilis'' Staunton ex D.Don) * ''Libocedrus plumosa'' (D.Don) Sarg. (as ''T. doniana'' Hook.) * ''Platycladus orientalis'' (L.) Franco (as ''T. orientalis'' L.) * ''Podocarpus javanicus'' (Burm.f.) Merr. (as ''T. javanica'' Burm.f.) * ''Tamarix aphylla'' (L.) H.Karst. (as ''T. aphylla'' L.) * ''Tetraclinis articulata'' (Vahl) Mast. (as ''T. articulata'' Vahl) * ''Thujopsis dolabrata'' (Thunb. ex L.f.) Siebold & Zucc. (as ''T. dolabrata'' Thunb. ex L.f.) * ''Widdringtonia nodiflora'' (L.) Powrie (as ''T. cupressoides'' L.) and many more ==Description== Thujas are evergreen trees growing from tall, with stringy-textured reddish-brown bark. The shoots are flat, with side shoots only in a single plane. The leaves are scale-like 1–10 mm long, except young seedlings in their first year, which have needle-like leaves. The scale leaves are arranged in alternating decussate pairs in four rows along the twigs. The male cones are small, inconspicuous, and are located at the tips of the twigs. The female cones start out similarly inconspicuous, but grow to about 1–2 cm long at maturity when 6–8 months old; they have 6-12 overlapping, thin, leathery scales, each scale bearing 1–2 small seeds with a pair of narrow lateral wings.〔 The five species in the genus ''Thuja'' are small to large evergreen trees with flattened branchlets. The leaves are arranged in flattened fan shaped groupings with resin-glands, and oppositely grouped in 4 ranks. The mature leaves are different from younger leaves, with those on larger branchlets having sharp, erect, free apices. The leaves on flattened lateral branchlets are crowded into appressed groups and scale-like and the lateral pairs are keeled. With the exception of ''T. plicata'', the lateral leaves are shorter than the facial leaves (Li ''et al.'' 2005). The solitary flowers are produced terminally. Pollen cones with 2-6 pairs of 2-4 pollen sacked sporophylls. Seed cones ellipsoid, typically 9-14mm long, they mature and open the first year. The thin woody cone scales number from 4-6 pairs and are persistent and overlapping, with an oblong shape, they are also basifixed. The central 2-3 pairs of cone scales are fertile. The seed cones produce 1 to 3 seeds per scale, the seeds are lenticular in shape and equally 2 winged. Seedlings produce 2 cotyledons.〔Flora of North America Editorial Committee. 1993. ''Pteridophytes and gymnosperms. Flora of North America north of Mexico, v. 2''. New York: Oxford University Press. ISBN 0-19-508242-7 Page 410.〕〔Henry A Gleason. ''New Britton and Brown Illustrated flora of Eastern North America and adjacent Canada Vol 1, The Pteridophya, Gymnospermae and Monocotyledoneae.'' Hafner Press, pp 58-67.〕 A hybrid between ''T. standishi'' and ''T. plicata'' has been named as the cultivar ''Thuja'' 'Green Giant'. Another very distinct and only distantly related species, formerly treated as ''Thuja orientalis'', is now treated in a genus of its own, as ''Platycladus orientalis''. The closest relatives of ''Thuja'' are ''Thujopsis dolabrata'', distinct in its thicker foliage and stouter cones, and ''Tetraclinis articulata'' (Greek ''θύια, θύα'', formerly classed in the genus and after which ''Thuja'' is named), distinct in its quadrangular foliage (not flattened) and cones with four thick, woody scales. The genus ''Thuja'', like many other forms of conifers, is represented by ancestral forms in Cretaceous rocks of northern Europe, and with the advance of time is found to migrate from northerly to more southerly regions, until during Pliocene time it disappeared from Europe. ''Thuja'' is also known in the Miocene beds of the Dakotas. 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「Thuja」の詳細全文を読む スポンサード リンク
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