Q.How does the structure of a fruit such as coconut assist its dispersal by water?

The coconut fruit is structurally well adapted for dispersal by water. Its middle fruit-wall layer, the mesocarp, is thick and composed of a mass of tough, fibrous tissue (the coir fibre familiar from coconut husks) rather than being fleshy or hard.

This fibrous mesocarp is lightweight relative to its bulk and traps a good deal of air within its structure, giving the whole fruit considerable buoyancy. As a result, a fallen coconut fruit can float on the surface of the sea (or a river) and be carried by water currents over very long distances -- sometimes across entire ocean stretches -- without the seed inside being damaged by prolonged immersion, because it remains protected within the hard inner endocarp (the familiar hard 'shell'). When the floating fruit eventual …

Identify the specific fruit-wall layer responsible (mesocarp), its structural property (thick, fibrous, air-trapping) and the fu …

Attributing buoyancy to the hard shell (endocarp) -- the shell protects the seed, but it is the fibrous, air-trapping mesocarp …