I can understand why a plant might want to surround its seeds with luscious fruit, but why would a plant surround its seeds with a wad of fibers? Anyone have any thoughts, information or educated guesses? Were the fibers a water trap maybe? But then how would the seeds get dispersed?
Birds value fibrous materials for nest making, thereby dispersing the seeds.
Many plants surround their seeds with fibers, and the seeds are then dispersed by the wind (e.g. cottonwood and milkweed).
It’s always wise to keep in mind that any domesticated plant, especially one like cotton that was domesticated a loooonnngggg time ago, has been bred like crazy, propaging bizarre but useful (or attractive, in the case of decorative plants) mutations, until they have diverged widely from the wild plants from whence they came.
So, my WAG (which I was unable to back up through some brief web searches, sorry) is that though the fibers in wild cotton seeds facillitated the distribution of seeds by wind, domestic plants have been bred for longer, stronger fibers, which cannot be caught by the wind as easily.
“cotton that was domesticated a loooonnngggg time ago”
See http://www.gardendigest.com/timegl.htm which shows that cottonwas grown in India for textile production at least as far back as 3500 BC.
The new world variety of the plant also has a history that goes back thousands of years.
It frequently takes only a few generations of selective breeding to cause large changes in a plants phenotype.
OK, granted, cotton today doesn’t look like its wild ancestor. It is still safe to assume that the wild ancestor had seeds surrounded by a significant amount of fiber. (If there weren’t a significant amount of fiber, the plant would not have attracted human attention in the first place.) So why the fiber? (And thanks for the educated guesses posted so far.)
By the way, is the wild ancestor of cotton still around?
I like Fear Itself’s explanation. I also found a web page that says:
Here are some pages with pictures of wild cotton, though I couldn’t find any nice images of seed pods filled with fiber:
http://www.ibiblio.org/herbmed/pictures/e-i-04.html
http://chili.rt66.com/hrbmoore/Images/D-G/Gossypium_thurberi-1.jpg
Thanks for the links, Podkayne.
I notice that wild cotton seems to be a desert plant. This might argue for my water-retention explanation. How about this scenario:
[ul][li]Cotton boll falls on the ground.[/li][li]Desert winds catch cotton fibers, blowing the bolls away and thus dispersing the seeds.[/li][li]When the rain finally comes, the cotton boll absorbs water, and holds it next to seeds, assisting germination.[/ul][/li]
Fear Itself’s bird nest explanation has some appeal at first glance. However, the water-retaining properties of cotton would make it unsuitable for lining a nest, would they not? (What bird wants a soggy nest?)