Sunday, December 27, 2009

Strangling fig

In Climbing Mount Improbable, Richard Dawkins describes strangling figs:
The story of the strangling figs is worth telling. The forest floor is a dark place, starved of solar energy. It is the goal of every tree in the forest to reach the open sky and the sun. Tree trunks are leaf-elevators, devices for lifting solar panels - leaves- above the shade of rival trees. Most trees are fated to die as saplings. Only when an adult tree in the immediate vicinity crashes down, overcome by gales and years, does a young sapling have its chance. At any one point in the forest, this lucky event may happen just once in a hundred years. When it does, there is a gold rush to the sun. All the saplings in the area, drawn from many species, enter a headlong race to be the one to fill the precious gap in the canopy.

But the strangling figs have discovered their own sinister short cut and their story would upstage the serpent of Genesis. Instead of waiting for an existing tree to die, they contrive the event. A strangling fig tree begins life as a climber. It wraps itself around an existing tree of another species and grows like a clematis or rambling rose. But, unlike a clematis, the strangling fig's tendrils continue to grow stouter and stronger. It relentlessly tightens its grip on the unfortunate host tree, preventing it growing and eventually achieving the botanical equivalent of throttling it to death. The fig tree has by now grown to a respectable height, and it easily wins the race to the patch of light vacated by the stifled tree. The banyan tree is a kind of strangling fig with an added, remarkable, feature. Having smothered its original host, it sends out aerial roots which, when they hit ground, become proper, absorbing roots but, above ground, serve as additional trunks. So the single tree becomes an entire wood which may be 1,,000 Feet in diameter and can provide shelter for a medium-sized covered market in India.
When someone mentions anything about MRI (even if it does not have anything to do with me) I am reminded of strangling figs. Thinking of lying in the narrow space inside an MRI machine makes me feel like the tree being smothered by a strangling fig.

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