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''Dioon'' is a genus of cycads in the family Zamiaceae. It is native to Mexico and Central America.〔(Kew World Checklist of Selected Plant Families )〕 Their habitats include tropical forests, pine-oak forest, and dry hillsides, canyons and coastal dunes.〔Christenhusz, M. J. M., J. L. Reveal, A. K. Farjon, M. F. Gardner, R. R. Mill & M. W. Chase. 2011. A new classification and linear sequence of extant gymnosperms. Phytotaxa 19: 55–70.〕〔Molina Rosito, A. 1975. Enumeración de las plantas de Honduras. Ceiba 19(1): 1–118.〕〔Vovides, A. P., J. D. Rees & M. Vázquez-Torres. 1983. Zamiaceae. Flora de Veracruz 26: 1–31.〕〔Breedlove, D.E. 1986. Flora de Chiapas. Listados Florísticos de México 4: i–v, 1–246.〕 Dioons are dioecious, palmlike shrubs with cylindrical stems, usually with many leaves. Leaf bases are persistent or shedding to leave smooth bark. The genus is commonly divided into two groups of distinct morphology. The first includes ''D. mejiae'', ''D. rzedowskii'', and ''D. spinulosum'', which are characterized by the greater size of their fronds, trunks, and cones. The second group contains ''D. califanoi'', ''D. caputoi'', ''D. edule'', ''D. holmgrenii'', ''D. merolae'', ''D. purpusii'', ''D. sonorense'', and ''D. tomasellii'', which are smaller overall, with shorter trunks, much shorter fronds, and smaller cones. The leaves are pinnate, spirally arranged, interspersed with cataphylls, with leaflets not articulated and lacking a midrib. The lower leaflets are often reduced to spines. The sporophylls are not in vertical rows in cones, and the megasporophyll apices are broadly flattened, upturned, and overlapping. ==Species== Species accepted:〔 #''Dioon angustifolium'' Miq. - Nuevo León, Tamaulipas #''Dioon argenteum'' T.J.Greg. & al. - Oaxaca # ''Dioon califanoi'' De Luca & Sabato - Puebla, Oaxaca # ''Dioon caputoi'' De Luca, Sabato & Vázq.Torres Puebla, Oaxaca # ''Dioon edule'' Lindl. - Nuevo León, Tamaulipas, Veracruz, Guanajuato, Chiapas, Hidalgo, Mexico State, Querétaro, San Luis Potosí # ''Dioon holmgrenii'' De Luca, Sabato & Vázq.Torres - Oaxaca # ''Dioon mejiae'' Standl. & L.O.Williams - Honduras # ''Dioon merolae'' De Luca, Sabato & Vázq.Torres - Oaxaca, Chiapas # ''Dioon purpusii'' Rose - Oaxaca # ''Dioon rzedowskii'' De Luca, Sabato & Vázq.Torres - Oaxaca # ''Dioon sonorense'' (De Luca, Sabato & Vázq.Torres) Chemnick ''et al.'' - Sonora, Sinaloa # ''Dioon spinulosum'' Dyer ex Eichl - Veracruz, Oaxaca #''Dioon stevensonii'' Nic.-Mor. & Vovides - Michoacán, Guerrero # ''Dioon tomasellii'' De Luca, Sabato & Vázq.Torres - Durango. Jalisco, Nayarit 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「Dioon」の詳細全文を読む スポンサード リンク
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