Someone lost in a forest need only study the trees around him carefully to find his way. In our hemisphere, he will find that the side of the tree with the most leaves and branches is the south side. Also, by checking the tops of the trees, he will find that they lean to the south too.
Another clue to direction is found in the bark, which is lighter and brighter on the south side. The stump of a cut tree is also a direction finder, for its rings provide a clue. The rings will be thinner on the south side and thicker on the north.
One more clue: moss growing at the base of a tree will be another sign, this one pointing to the north.