Christmas Bells

Christmas Bells
Christmas Bells - Blandfordia nobilis

Thursday, September 27, 2007

Spring Photo Competition - at the CTC@Robertson

Entries for the Robertson CTC's Spring Photo competition have closed (officially), but I guess we can squeeze in a few last minute entries if you feel inspired. But be quick!

I have entered one of the Gnome series shown a few days ago. And I have also entered a photo of a frond of a Soft Tree Fern (Dicksonia antarctica) unfurling. This photo was taken several days ago, at George's place. He has many Tree Ferns there, including both the two main local species - this one and the "Rough Tree Fern" (Cyathea australis).

The distinctive shape of the Tree Fern frond, as it grows, and unfurls progressively is really interesting. Historically they are called "crosiers" which is the name of a Bishop's symbolic staff - the so called "Shepherd's Crook" - named after the traditional staff used by shepherds, looking after their roaming flocks of sheep and/or goats. The hook in the top was supposed to help the Shepherd retrieve a lost sheep. All of that imagery has been borrowed by the Church as symbolic of Christ, the "Good Shepherd". And that is why the "crosier" is used for the symbol of power and authority of a Bishop.
But mathematicians and theoretical physicists have also focussed on the Fern Frond, as it unfurls, as a demonstration of "chaos theory" - for within each frond are smaller and smaller leaf sections, each of which as it grows, reveals the repetitive patterns which first prompted mathematicians to describe the seemingly endless repetitive sequences which are key to chaos theory. Obviously, in the Tree Ferns, these pattern repeats are not infinite, but the leaves are so large, and so complex in structure, that they are probably the supreme example in the plant world of complex leaf structures. The structure is described as multiple-pinnate, which literally means "feathered upon feathered" leaves.

There is an interesting description of this unfurling processes of Tree Fern branches in Wikipedia, where they describe it as "circinate vernation" - a term which is new to me.

I love these Tree Fern fronds, and I know that Crimson Rosellas also love them. They eat Tree Fern fronds, much as we humans eat Asparagus.
These photos were taken at the Australian National Botanic Gardens, Canberra, where they have a fantastic display of the Soft Tree Ferns growing in the rainforest gully. There is one point where the Tree Ferns are growing underneath a foot bridge, and one can often see Crimson Rosellas sitting in the Tree Ferns, chewing the young growth of the fern leaves, as in these photographs.

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