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{{Taxobox
| color = lightgreen
| name = ''Dryas octopetala''
| image = mountainavens2.jpg
| image_width = 250px
| regnum = [[Plant]]ae
| divisio = [[Flowering plant|Magnoliophyta]]
| classis = [[Magnoliopsida]]
| ordo = [[Rosales]]
| familia = [[Rosaceae]]
| genus = ''[[Dryas (plant)|Dryas]]''
| species = '''''D. octopetala'''''
| binomial = ''Dryas octopetala''
| binomial_authority = [[Carolus Linnaeus|L.]]
}}
[[Image:Dyas octopetala seed head.jpg|left|thumb|220px|Seed head of ''Dryas octopetala]]
'''''Dryas octopetala''''' ([[common name]]s include '''mountain avens''', '''white dryas''', and '''white dryad''') is an [[arctic-alpine]] [[flowering plant]] in the [[family (biology)|family]] [[Rosaceae]]. It is a small prostrate [[evergreen]] [[subshrub]] forming large colonies, and is a popular flower in [[rock garden]]s. The [[specific epithet]] ''octopetala'' derives from the [[Greek language|Greek]] ''octo'' (eight) and ''petalon'' ([[petal]]), referring to the eight petals of the flower, an unusual number in the Rosaceae, where five is the normal number. However flowers with up to 16 petals also occur naturally.
''Dryas octopetala'' has a widespread occurrence throughout mountainous areas where it is generally restricted to [[limestone]] outcrops. These include the entire [[Arctic]], as well as the mountains of [[Scandinavia]], the [[Alps]], [[Carpathian Mountains]], [[Balkans]], [[Caucasus]] and in isolated locations elsewhere. In [[Great Britain]], it occurs in the [[Pennines]] (northern [[England]]), at two locations in [[Snowdonia]] (north [[Wales]]), and more widely in the [[Scottish Highlands]]; in [[Ireland]] it occurs on [[The Burren]] and a few other sites. In [[North America]], it reaches as far south as [[Colorado]] in the [[Rocky Mountains]].
The stems are woody, tortuose, with short, horizontal rooting branches. The [[Leaf|leaves]] are glabrous above, densely white-[[tomentose]] beneath. The [[flower]]s are produced on stalks 3-10 cm long, and have eight creamy white petals. The style is persistent on the [[fruit]] with white feathery hairs, functioning as a wind-dispersal agent. The feathery hairs of the sea head first appear twisted together and glossy before spreading out to an expanded ball which the wind quickly disperses.
It grows in dry localities where snow melts early, on gravel and rocky barrens, forming a distinct heath community on calcareous [[soil]]s.
==Climatology==
The [[Younger Dryas]] and [[Older Dryas]] [[stadial]]s are named after ''Dryas octopetala'', because of the great quantities of its [[pollen]] found in cores dating from those times. During these cold spells, ''Dryas octopetala'' was much more widely distributed than it is today, as large parts of the [[northern hemisphere]] that are now covered by [[forest]]s were replaced in the cold periods by [[tundra]].
==Gallery==
<gallery>
Image:mountainavens3.jpg
Image:Dryas_octopetala_Liechtenstein.jpg
Image:Dryas_octopetala_a4.jpg
</gallery>
[[Category:Rosaceae]]
[[Category:Alpine flora]]
[[Category:Arctic flora]]
| color = lightgreen
| name = ''Dryas octopetala''
| image = mountainavens2.jpg
| image_width = 250px
| regnum = [[Plant]]ae
| divisio = [[Flowering plant|Magnoliophyta]]
| classis = [[Magnoliopsida]]
| ordo = [[Rosales]]
| familia = [[Rosaceae]]
| genus = ''[[Dryas (plant)|Dryas]]''
| species = '''''D. octopetala'''''
| binomial = ''Dryas octopetala''
| binomial_authority = [[Carolus Linnaeus|L.]]
}}
[[Image:Dyas octopetala seed head.jpg|left|thumb|220px|Seed head of ''Dryas octopetala]]
'''''Dryas octopetala''''' ([[common name]]s include '''mountain avens''', '''white dryas''', and '''white dryad''') is an [[arctic-alpine]] [[flowering plant]] in the [[family (biology)|family]] [[Rosaceae]]. It is a small prostrate [[evergreen]] [[subshrub]] forming large colonies, and is a popular flower in [[rock garden]]s. The [[specific epithet]] ''octopetala'' derives from the [[Greek language|Greek]] ''octo'' (eight) and ''petalon'' ([[petal]]), referring to the eight petals of the flower, an unusual number in the Rosaceae, where five is the normal number. However flowers with up to 16 petals also occur naturally.
''Dryas octopetala'' has a widespread occurrence throughout mountainous areas where it is generally restricted to [[limestone]] outcrops. These include the entire [[Arctic]], as well as the mountains of [[Scandinavia]], the [[Alps]], [[Carpathian Mountains]], [[Balkans]], [[Caucasus]] and in isolated locations elsewhere. In [[Great Britain]], it occurs in the [[Pennines]] (northern [[England]]), at two locations in [[Snowdonia]] (north [[Wales]]), and more widely in the [[Scottish Highlands]]; in [[Ireland]] it occurs on [[The Burren]] and a few other sites. In [[North America]], it reaches as far south as [[Colorado]] in the [[Rocky Mountains]].
The stems are woody, tortuose, with short, horizontal rooting branches. The [[Leaf|leaves]] are glabrous above, densely white-[[tomentose]] beneath. The [[flower]]s are produced on stalks 3-10 cm long, and have eight creamy white petals. The style is persistent on the [[fruit]] with white feathery hairs, functioning as a wind-dispersal agent. The feathery hairs of the sea head first appear twisted together and glossy before spreading out to an expanded ball which the wind quickly disperses.
It grows in dry localities where snow melts early, on gravel and rocky barrens, forming a distinct heath community on calcareous [[soil]]s.
==Climatology==
The [[Younger Dryas]] and [[Older Dryas]] [[stadial]]s are named after ''Dryas octopetala'', because of the great quantities of its [[pollen]] found in cores dating from those times. During these cold spells, ''Dryas octopetala'' was much more widely distributed than it is today, as large parts of the [[northern hemisphere]] that are now covered by [[forest]]s were replaced in the cold periods by [[tundra]].
==Gallery==
<gallery>
Image:mountainavens3.jpg
Image:Dryas_octopetala_Liechtenstein.jpg
Image:Dryas_octopetala_a4.jpg
</gallery>
[[Category:Rosaceae]]
[[Category:Alpine flora]]
[[Category:Arctic flora]]