Chicken of the woods is an edible mushroom that tends to grow on dying oak trees in the Hillcountry. It appears in the summer and requires dark and damp conditions to grow. It has a springy texture somewhat like raw chicken and may be a good substitute for chicken in dishes for flavor. For further reading and a recipe, see this excellent page.
Chicken of the woods grows quite quickly. Each picture below was taken about 24 hours apart. As you can see, the mushroom at the top goes from approximately 4 inches in diameter to somewhere around 10 to 12 inches in diameter over the course of 3 or 4 days.