I don't recommend doing this, but I do recommend watching it. A couple of people set fire to one edge of a drift of cottonwood seeds. The fire travels slowly from one side of the drift to the other, leaving the grass underneath it unburned.
I guess you could take a few scientific lessons from this. Perhaps something about how fire requires oxygen, and oxygen requires surface area. Because the fluff is fine, it intermingles with the air required to keep it burning. It also helps that the fluff is drier than the grass it lies on.
Mostly, though, this is an incredible video to just to sit and watch, as the seeds and their carrier fluff go up in smoke while the grass stays green and living. Watching the line of fire advance so quickly is also mesmerizing. The video reminds me of seeing a friend of mine, who happened to be in the middle of a hair-cutting session outside, near a flaming grill. (I don't know why, either. Don't worry, there was no meat on the grill.) She made a wide gesture with a hand full of hair, and fwoof. She was holding a handful of fire. The woman had very fine hair. Despite the fact that it all went up within a couple of seconds, she didn't have more than a little redness on her hand.
Anyone seen this, or something like it, in real life?