Socratea exorrhiza, the walking palm or cashapona, is a palm native to rainforests in tropical Central and South America. It can grow to 25 metres in height, with a stem diameter of up to 16 cm, but is more typically 15–20 m tall and 12 cm in diameter. It has unusual stilt roots, the function of which has been debated. Many species of epiphyte have been found growing on the palms. The palm is pollinated by beetles, and various organisms eat its seeds or seedlings.
Function of stilt roots
A close up view of the stilt roots
How the stilt roots were proposed to allow it to right itself after other plants collapse on it. 1 - the palm is growing normally. 2 - a tree collapses onto the palm and flattens the stem. 3 - new stilt roots form along the old stem and the original roots (dashed lines) start to die. 4 - the palm continues to grow normally but has now moved away from where it originally germinated
E. J. H. Corner in 1961 hypothesised that the unusual stilt roots of S. exorrhiza were an adaptation to allow the palm to grow in swampy areas of forest. No evidence exists that stilt roots are in fact an adaptation to flooding, and alternative functions for them have been suggested. John H. Bodley suggested in 1980 that they in fact allow the palm to "walk" away from the point of germination if another tree falls on the seedling and knocks it over. If such an event occurs then the palm produces new vertical stilt roots and can then right itself, the original roots rotting away. Radford writes in the Skeptical Inquirer in December 2009 that "As interesting as it would be to think that when no one is around, trees walk the rainforest floor, it is a mere myth", and cites two detailed studies that came to this conclusion. Other advantages of stilt roots over normal roots have since been proposed. Swaine proposed in 1983 that they allow the palm to colonise areas where there is much debris (for example, dead logs) as they can avoid it by moving their roots. Hartshorn suggested in 1983 that...
