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Saxifraga osloënsis [Oslo Saxifrage]


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Rørslett, B. 2013. Saxifraga osloënsis G.Knaben (Saxifragaceae). Flowers photographed in visible and ultraviolet light. http://www.ultraviol...raga-osloensis/

 

Saxifraga osloënsis G.Knaben

NO: Oslosildre

SE: Hällebräcka

DK: Oslo-Stenbræk

 

Described a new species as late as in 1954, S. osloënsis is endemic to the inner Oslo Fjord in Norway and a narrow adjacent area eastwards in Sweden. It is considered an alloploid (2n=44) resulting from chromosome doubling in a hybrid between S. adscendens L. and S. tridactylites L. (Knaben 1954). It exhibits characters from both putative parents and has by and large the same ecology as these two. In the Oslo Fjord region it grows on thin soils overlaying calcareous rocks in alvar-like vegetation. S. tridactylites frequently is associated with it and these taxa are sometimes difficult to keep apart in the field without access to capsule and seed features. However, S. osloënsis can usually be recognised by its taller and more sturdy stature and petals that are at least three times the sepals in length. Furthermore it has a well defined rosette with each leaf having 3(-7) lobes, the mid lobe being the largest of them.

 

Plants photographed in situ in the Inner Oslo Fjord, Norway 18 May 2013.

 

This is the general habitus of this species. Here it grows in an alvar-like habitat with open vegetation.

 

SAXI_OSL_B1305183130_VIS_HABITUS.jpg

Image reference: AXI_OSL_B1305183130_VIS_HABITUS.jpg

Visible light: Nikon D300, Medical-Nikkor 120 mm f/4 lens, built-in ring flash.

 

SAXI_OSL_B1305183139_VIS.jpg

Image reference: SAXI_OSL_B1305183139_VIS.jpg

Visible light: Nikon D300, Medical-Nikkor 120 mm f/4 lens, built-in ring flash.

 

The flowers are quite small,

 

SAXI_OSL_I1305180586_UV.jpg

Image reference: SAXI_OSL_I1305180586_UV.jpg

Ultraviolet light: Nikon D3200, UV-Nikkor 195 mm f/4.5 lens, Baader U 2"(Venus) filter, SB-140 flash.

 

The petals are densely covered by conical cells The tiny nectaria are somewhat UV reflective.

 

References:

Knaben, G. 1954. Saxifraga osloënsis n.sp. a tetraploid species of the Tridactylites section. Nytt Magasin Bot. 3: 117-138.

 

[Published 20 May 2013]

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