February 24, 2004
A small Lichen on an ash tree near Little Fresh Pond.
At the Reservation, lichens can be found on many of the trees, which they do not harm.

Lichens are an unusual life form. They are composed of two unrelated organisms, a fungus and one or more types of alga. The algae provide food for the fungus, and the fungus provides structure and support for the algae.

Lichens do most of their growing in the winter, especially when they are wet. During dry, hot summer weather they become dormant. They are especially sensitive to air pollution, and are used worldwide as indicators of air quality