Micranthes Stellaris

''Micranthes stellaris'', synonym ''Saxifraga stellaris'', the starry saxifrage or hairy kidney-wort, is an Arctic–alpine species in the family Saxifragaceae. It produces panicles of 5–10 white flowers on a stem up to tall, rising from a basal leaf rosette. One subspecies is found from eastern Canada to Russia, including the British Isles, while another is found in the mountains of southern Europe.

Description

''Micranthes stellaris'' grows as a leaf rosette, which produces a generally leafless stem up to tall. The leaves are toothed and somewhat fleshy, ovate or obovate, and without an obvious petiole. They are typically long (varying from ), with a cuneate (wedge-shaped) base.

The flowers are borne in a loose panicle comprising 5–10 flowers; each flower has deflexed sepals, surrounding five white petals, long, with two yellow or red spots near the base. The anthers are also red or yellow. Flowers are borne from June to August.

The seeds are dark brown, glabrous, long, and wide. They are elliptic, ovoid or reniform in shape, with longitudinal ribs bearing spines. ''M. stellaris'' has a chromosome number of 2''n'' = 28.

Taxonomy

''Micranthes stellaris'' was first described by Carl Linnaeus in his 1753 work ''Species Plantarum'' as ''Saxifraga stellaris''. Linnaeus noted the species' occurrence in the mountains of Spitsbergen, Lapland, Switzerland, Styria and Westmorland. The nominate subspecies, ''Micranthes stellaris'' subsp. ''stellaris'' is the northern subspecies, occurring from Canada to Russia, including the British Isles. The subspecies in the Alpide belt and other mountains in southern Europe is often called ''M. stellaris'' subsp. ''alpigena'', but an older name has priority – ''M. stellaris'' subsp. ''robusta''. The name ''M. stellaris'' subsp. ''prolifera'' is used for plants from the south-eastern Alps which have few flowers but produce bulbils along the stems.

Distribution and ecology

''Micranthes stellaris'' has an Arctic–alpine distribution. It is found from Baffin Island, Labrador and Greenland to Arctic Russia, including Iceland, Scandinavia and the British Isles. Further south, it is found from the Sierra Nevada in southern Spain to the eastern Carpathians, including lower ranges such as the Massif Central.

In the Arctic, ''M. stellaris'' may occur down to sea level. Within the British Isles, ''M. stellaris'' is abundant in North Wales, Northern England and Scotland, reaching the summit of Ben Nevis (), but is only found locally in Ireland. Its southernmost stations in Great Britain are the slopes of Plynlimon and the Rheidol valley; it does not occur in the mountains of South Wales. In the Vosges, it occurs around , but only rarely below in the Swiss Alps. In the Sierra Nevada of southern Spain, it lives at up to .

''Micranthes stellaris'' lives in damp environments, such as wet flushes, beside streams or springs, or on wet rock ledges. It is self-compatible, but its flowers are protandrous, and are usually pollinated by flies.

References

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{{Taxonbar, from1=Q18121653, from2=Q162521

stellaris
Flora of Northern Europe
Flora of Subarctic America
Flora of Southwestern Europe
Alpine flora
Plants described in 1753
Taxa named by Carl Linnaeus