Saturday, 7 March 2009

Darwin's Garden

[Photo: Orchids were Darwin's sometime favourite plants - this is the Crimson Spider Orchid, Caladenia (or Arachnorcis if you like) concolor, from The Monk, near Castlemaine in Victoria, 1997]

I've just finished preparing my talk for a Royal Botanic Gardens Foundation event to be held on Tuesday night. The title is 'Darwin's Garden' and, you guessed it, it's about Darwin and his garden. Not just his quite famous garden at Down (without an 'e') House in Downe, but also world's flora - once the garden of creation, now the garden of evolution.

I'll talk about Darwin's abiding interest in plants generally, and his particular love of animal-eating plants and orchids. He once said 'I care more about Drosera [an insect-eating plant] than the origin of all the species in the world'. Perhaps a little hyperbole, but Drosera is a fun plant. Most of the 170 species grow in Australia so it's something special for us too.

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. 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 include 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 glued to various appendages of your recently visiting insect.

I'll also talk about the kind of logic Darwin used in arguing the case of 'natural selection' - giving a couple of plant examples of course. And where's Wallace? Well Darwin and Wallace found a way to work together. Darwin used Wallace's 'term's as his chapter headings. Wallace put out a 'wanted poster' for a moth with a 30 cm long proboscis (straw-like device for sucking up nectar) that Darwin had hypothesised must exist when he saw an orchid from Madagascar (see my blog photograph for me peering into one) with a 30 long nectar spur.

To end, I'll talk about the latest classification of life - that is, where we've taken Darwin's central idea. Of course most of life is small and unseen (as I read recently in the New Scientist , and may have mentioned before, 'to the closest approximation, life is unicellular').

Naturally I'll encourage a walk through our quote smitten, mirror-letters that spell out the word Darwin (just inland of the Children's Fig and to the south of the Twin Ponds).

2 comments:

Mary said...

Sounds like a great talk. Any chance you'll post it?

Tim Entwisle said...

I'll see what I can do. The powerpoint pictures will only tell half the story but might be interesting (no fully written version).