Saturday, 1 August 2009

Darwin's Garden (P4P*)


In his later years, Charles Darwin experimented and observed nature in his backyard and glasshouse ‘laboratory’ at Down House in Downe, England. He studied pollination, climbing vines, insect-eating plants, and famously, earth worms, among other things.

His other ‘garden’ was the entire flora of the world, as observed and collected during the voyage of the The Beagle between 1831 and 1836. After the publication of The Origin of Species in 1859, this garden of creation became the garden of evolution.

This year we have been celebrating the 200th birthday of Charles Darwin and 150 years since the publication of his famous theory of evolution by natural selection.

One of the things we’ve tried to emphasise here at the botanic gardens – and you can see a reference to this in the quotes adorning our D-A-R-W-I-N installation – is Darwin's abiding interest in plants generally, and his particular love of animal-eating plants and orchids. (The picture above is the back of the letter ‘D’, featuring Darwin’s head!).

Darwin once said 'I care more about Drosera [the insect-eating sundews] than the origin of all the species in the world'. Perhaps a little hyperbole, but for someone who wasn’t all that taken by the Australian flora he fell in love with a genus of about 180 species, more than half of which are native to our country (mostly in south-western Australia). (Although he said he looked forward 'with more pleasure to seeing Sydney than to any other part of the voyage', he left saying famously 'I leave your shores without sorrow or regret’.)

He also said 'I never was more interested in any subject in my life than this of orchids'. Clearly he'd forgotten all about his sundews, but orchids certainly gave him lots of evidence for evolution and he published a major tome on how orchids and insects help each other, called The various contrivances by which orchids are fertilised by insects.

Those contrivances included trigger mechanism to bash the head of the insect against ready waiting pollen, buckets to trap the insect and direct it past the pollen, and long nectary spurs that require the insects to dip their head deep in the spur to get the sugary reward, thus....past the pollen again. Actually the pollen in orchids is glued together in a big lump called a 'pollinium', which can found attached to various appendages of your recently visiting insect.

Most famously, Darwin predicted the existence of a moth with a 30 cm long proboscis (straw-like device for sucking up nectar) after he saw an orchid from Madagascar with a 30 long nectar spur. 41 years later, and after his death, such a moth was discovered.

Here in the botanic garden you can walk along our Thinking Path, reading and contemplating the quotes about evolution. Every tree in the botanic garden can remind you of the tree of life, with the leaves representing species alive with us today.

It’s worth remembering, though, that most species are extinct, and most of life is unicellular. That is, to continue the analogy, most leaves have fallen off the tree and only a few of these leaves represent the flowering plants and largish animals we see around us every day.

And to learn more about Darwin and his legacy, visit the Darwin’s Descendants – 200 years of scientific adventure exhibition in the Red Box Gallery, on the left past the Art Gallery of NSW, from August 3 until November 24 (weekdays 10 am to 4 pm, free entry). There will also be Science Open Days at the Gardens on the weekend of 23 and 24 August 2009.

The back of the letter ‘D’, featuring Darwin’s head, and the first letter in the DARWIN installation at the Royal Botanic Gardens]

*This Passion for Plants posting will also appear on the ABC Sydney website (possibly under 'gardening'), and is the gist of my radio interview with Simon Marnie on Saturday Morning sometime between 9-10 am on 702AM.

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