Keith.
Back in the 18th century extra supplies of gunpowder were carried in bags of leather or a tight weave linen. These bags are lighter to carry in a pack than carrying extra powder horns. Some woodsmen used these bags once empty for storing spare plant & fungi tinders for flint & steel fire lighting.

I have 5 of these greased leather gunpowder bags.
“…fungus that grows on the outside of the birch-tree…used by all the Indians in those parts for tinder…called by the Northern Indians Jolt-thee, and is known all over the country bordering on Hudson’s Bay by the name of Pesogan…there is another kind…that I think is infinitely preferable to either. This is found in old decayed poplars, and lies in flakes…is always moist when taken from the tree but when dry…takes fire readily from the spark of a steel: but it is much improved by being kept dry in a bag that has contained gunpowder.”
~Samuel Hearne, Northern Canada, 1772