I was out by the St Johns river the other day and finally got around to gathering some cottonwood inner bark. This is from a dead standing tree. Even still, its moist because of all the dew and frost lately. I spread it out in a soda flat to dry next to the fireplace. This stuff is great for flint and steel with char cloth. It takes flame quickly. I shred it fine and I hear if you powder it you can get a glowing coal from a ferro cerium rod. Some folks have made cordage from the live inner bark. I can see how that would work, this stuff being so fibrous. Carvers look for the thick bark, 2-6" thick, for carving material. A small chunk of bark makes a very good hand hold for bow drill fire making. I have one that is at least 10 years old and has no wear but a nice shiny polish where the spindle fits.
I like to store up nice, dry tinder for my trips into the boonies. I have those little snack size zip locks with birch bark, cottonwood inner bark, cedar/juniper inner bark, and some other natural tinders I've gathered. I throw two or three of these into my pack and no matter what the conditions, I have dry tinder.
Another tinder I gathered at the same place is a half dozen shelf fungus from a dead cottonwood log. These are polypore fungus but I don't know what species. I've been told they are good for catching spark. I can't wait till they are bone dry and I can experiment. They were dead and dry when I found them but they still have some moisture from the damp weather. They, too, are drying by the fireplace. I'll post my results with this experiment and any further information I discover.