Crampball fungus or King Alfreds cakes (Daldinia concentrica) is an excellent fungus to use as a tinder. They will take the sparks straight from a flint and steel as well as being realy good to make coals on the fire. Be warned though they burn VERY hot and Quickly turn to glowing coal. They grow on dead Beach trees mainly but also on other wood. The pic I have shown here is the tinder as it appears underneath showing the concentric rings so it is easy to ID. This glowing coal I show here took the spark directly from my flint. Bear in mind the fungus MUST be compleyely dry to do this.
Just like to add that you should only pick them when they are black,if they are brown they have not dropped the spores yet so should be left alone.