This stringy-looking lichen was photographed on the Cypress Grove Trail, but you'll also find a lot of it on the Lace Lichen Trail which parallels the main road from the entrance into the park. The lace lichen (which is often mistaken for Spanish moss) takes up residence on dead branches and it doesn't harm the rest of the tree.
Lichen are cooperative organisms formed from a fungus which provides the framework and an algae which provides the food.

Deer like to eat the lace lichen and birds use it to make nests. Lichen can absorb compounds from the air and are sensitive to pollutants, so their presence is a sign of good air quality.