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Argyroxiphium
''Argyroxiphium'' is a small genus of plants in the sunflower family, Asteraceae.〔(Candolle, Augustin Pyramus de. 1836. Prodromus Systematis Naturalis Regni Vegetabilis 5: 668 )〕〔(Tropicos, ''Argyroxiphium'' DC. )〕 Its members are known by the common names of silversword or greensword due to their long, narrow leaves and the silvery hairs on some species. It belongs to a larger radiation of over 50 species, including the physically different genera ''Dubautia'' and ''Wilkesia''. This grouping is often referred to as the silversword alliance.
== Description ==
These perennials are endemic to Hawaii, occurring only on the islands of Maui and Hawaii in an extremely localized distribution. They are primarily found above in elevation in alpine deserts or bogs, indicating an adaptation to low-nutrient soils. The Kaū or Mauna Loa Silversword (''A. kauense'') is the most adaptable: it can be found in rocky lava flows, bogs, and open forest.
They consist of rosette-forming epigeal shrubs or dwarf shrubs. They may consist of a single large rosette (Mauna Kea and Haleakalā silverswords), a short-branched rosette (Mauna Loa Silversword), or spreading with runners (Eke Silversword, greenswords). The flower heads consist of a ring of pistillate ray florets around 30 to 600 disk florets. The corolla varies in color from purplish to wine red or yellow, while the anthers are dark. A rosette will grow from 5–20 years before flowering, after which it dies. For those with a single rosette, this means the death of the plant (in contrast, those reproducing by runners rarely flower and may be very long-lived). Because they require cross-pollination by insects, many plants must flower at the same time in relatively close proximity or they will fail to set seed. A significant population must exist for enough to flower each year for pollination to occur.
Despite appearances, they are very closely related to the genus ''Dubautia''. Although some ''Dubautia'' are radically different from silverswords, those found in wet forests and alpine deserts clearly grade into the form of silverswords. Hybrids between ''Argyroxiphium sandwicense'' and ''Dubautia menziesii'' are common in Haleakalā Crater. Although the two species are quite distinct, the hybrids span the entire range of variation between them.
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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