Deer lichen is commonly called "reindeer moss," "deer moss," "powder-puff lichen", or "fairy pillows." It is a small, spongy pale sea-green plant. Various species live all over the world, from here to New Zealand and the Arctic circle. Treasure it because its presence means the air is good. When dry it is light and brittle; when wet it is soft and more richly colored.
When you're walking on a forest trail, you'll see its sea-foam form lining the path and spreading like surf over the forest floor, in places where it can get some sunlight.
It is part fungus, part alga. These two partners form what's called a symbiotic relationship: that is, neither the fungus nor the alga can live alone. The fungus or mycobiont provides shelter, the physical structure, and brings in moisture and minerals. The alga or photobiont turns light into food for the fungus by photosynthesis. Together they are symbionts.
It is used in architectural models and for crafts, and it provides food for wildlife. Deer lichen is sensitive to chemicals like sulfur dioxide and fertilizer so it is a good indicator of pollution. Also, it absorbs radiation from nuclear power plants. Deer lichens hold sand in place and help in forming new soil. Who knows what purpose it serves in nature or what we might find with greater study?
Where undisturbed, they could be 100 years old since they grow slowly - perhaps 1 mm a year.
There are two (some say eight) local species of deer lichen (Cladoniaceae). They are the fruiticose type: shrub-like and branching. Cladonia evansii is in puffs. Cladonia subtenuis is in mounds. See Lichen ID.
In Lookout for 2007, there are links, maps, descriptions, photos, and movies of local sites. Click on the Lookout 2008 - MindField icon or Lookout 2010, MindField 2012 for art fiction, imaginative fantasies, What's New on Earth Day 2010 -Eglin AFB sites and causes. Click Lookout 2009 - Deer Lichen Perspectives for timeline and identification topics, including this FAQ. Click Estuary Festival 2011 for spreading deer lichen.