Why do coconuts have "hair"?

I just saw this question posed by a child in a short story. The parents did not give a satisfactory answer, so now it has me wondering.

From reading wiki I gathered that it’s called coir, and that it may protect the inner coconut against salt water, but wouldn’t the outer shell already do that? Is there a reason for it, or is it just a by product of some other process? Do other plants have similar structures and, if so, for what purpose?

the ‘nut’ part of a coconut (i.e. the wooden shell bit) is encased in a thick layer of matted, fibrous husk, enclosed within a waxy skin. This enables coconuts to survive long enough in sea water to float off and germinate elsewhere, on a different land mass - the low density of the fibrous layer provides buoyancy as well as protection.

Coconuts are palms - and if you look at other palm species, they typically have similar sorts of seeds - a hard seed enclosed in a fibrous outer fleshy layer. In the case of dates, the fleshy layer is saturated with sugars, but the basic design of the fruit is similar.

Mangetout has it right.

Check at lower right in the illustration on this Wiki page to see a cross section of a coconut in its husk, which is what makes it capable of floating vast distances to pitch up on new shores. A husked coconut typically retains a few fibers of its formerly large husk.

Yeah, but the above doesn’t really explain why the hairs make a coconut more likely o deliver its genetic information intact after several days or weeks at sea.

My wag: it’s our good friend surface to volume ratio. The hairs increase the surface area, thus slowing down salt water transmission to the core.

Of course, this theory can be falsified if coconut hairs can be shown to absorb and transmit, rather than repel, fluid.

Speaking of coconut hair, how do you pronounce “coir?” Is it like choir? Or core? Or coy-er? Or does it rhyme with noir?

No - the “hairs” are the few remnant fibers that remain after the husk has been stripped off. When the coconut falls from the tree the husk is intact, and all its many hairs are enclosed in a smooth and fairly watertight skin.

That’s how I’ve always heard it.

Second photo on this page shows several nearly mature coconuts on a palm tree. Obviously, these have not yet been husked.

Last I heard, a coconut is a type of fruit called a drupe. So are peaches and cherries- the juicy part of the peach is derived from the same flower tissues as the husk of a coconut. A drupe sort of between the two extremes is a black walnut.

Isn’t it just nature’s equivalent of foam - for buoyancy?

Yes. The hairs,/fibres are just something that the palm family had in its toolbox. Other plants provide flotation for their seeds by means of enclosed air pockets, waxes and oils, etc.

“Coy-er” is closest: /ˈkɔɪr/ . Definitely not rhyming with noir, it’s not French, it’s derived from Tamil kayaru

Although it’s worth mentioning that the fibrous covering also provides padding - so the coconut can survive the drop to ground and potential bashing against rocks when coming ashore elsewhere.

The fibre seems to function primarily as a shock absorber.

Because coconuts need to be able to germinate and survive on sand that is mineral deficient, saline and with almost no water holding capacity, the embryo is provided with a huge endosperm to allow it to establish. That includes a large water reserve.

The coconut seed has consequently become huge and hollow, to the extent that it would smash to pieces when it fell from the tree, if it were not wrapped in protective padding.

The fibre certainly isn’t needed for bouyancy. A husked coconut seed is considerably more bouyant than fruit complete with fibre.

The fibre isn’t especially hydrophobic or hydrophilic. When you pick up a coconut from the ocean, the fibre is typically wet, but not so much that you can wring it out. It’s just typical plant fibre, which doesn’t seem to play any role at all in water movement.

Coir doormats are common enough in any hardware store. You can get one yourself and wet it to see how the fibre responds to water.

Yup. Coy, as in pretending to be shy and err, as in to make a mistake. You err when you are coy about coir. I think every doormat in India - or at least in the south - is made of coconut fibre (from the Dept. Of Random Information Online).

That’s it, like “Blake” mentions, the “Coir” is mainly a shock absorber, the nut’s you are buying for eating did not mature enough for the nut to full down from the tree on it’s own, it was harvested.
When the nut get’s ready to fall down on it’s own, it is already pretty brown and the outer skin is very tough, we have trees that are about 20 meters high and the nuts survive the fall undamaged even on rock or hard soil. I have seen trees a 100 years old and 50 meters high and even those nuts survived the fall…

Googling supports this.