Did you know that California has a state lichen? I didn't either, and it turns out that we've had one for over a year! In January of 2016, California became the first state to adopt an official state lichen, and Ramalina menziesii joined the ranks of the California poppy (Eschscholzia californica), the California quail (Callipepla californica), the coast redwood (Sequoia sempervirens), and the extinct-in-the-wild California grizzly bear (Ursus californicus) as official symbols of the Golden State.
Lichens are strange beasts, resulting from a symbiosis between two very different organisms, an alga (or in some cases a cyanobacterium) and a fungus. They are photosynthetic like plants and algae thanks to the algal/cyanobacterial partner in the symbiosis, but do not have roots or leaves. The fungus component restricts them to places where fungi can live, which means you generally don't find lichens in very dry places. That said, some lichens have adapted to live in hostile habitats such as the Arctic tundra and arid deserts. Many of them live on trees and other plants, but when they do so they are not parasitic. They can grow on nonliving surfaces such as rocks, buildings, and soils. Lichens are crucial players in the ecological process of primary succession, which occurs when virgin habitat is newly opened up to colonization by life (for example, the area left scoured by a retreating glacier, or land formed by recent lava flowing into the sea). The fungal partner of a lichen sends out hyphae which burrow into rock, eventually weakening it and forming soil. Plants cannot take root until soil is present, so lichens, in addition to being among the first organisms to colonize an area, modify the habitat to enable other species to become established.
In some ways, the fungus partner of a lichen can be viewed as a farmer, in the sense that it houses photosynthetic symbionts that do the hard work of fixing carbon into molecules such as sugars, which can then be used to fuel the fungus's metabolism. The fungus doesn't just mooch off its symbionts, though. As in other symbiotic relationships between unicellular algae and multicellular hosts, the fungus provides a safe place for the algae to live, as well as a stable environment in which to carry out its photosynthetic magic.
Most lichens have a simple morphology, growing as a crust over the substrate. Ramalina menziesii has a lacy morphology and typically lives as an epiphyte, draping over the branches of trees and shrubs. It is often associated with oak trees in California, especially the Coast Live Oaks (Quercus agrifolia) that live in the more humid regions along the coast. During the drought there was much less Ramalina hanging from the thirsty oak trees, but this year there does seem to be more of it. Strands of R. menziesii are used as nesting material by many birds, and I've seen deer eating whole gobs of the stuff, pulling it off the trees with their rubbery lips.
Ramalina menziesii is often referred to as "Spanish moss" which is misleading on any number of counts. First of all, it's not Spanish, being a species native to the west coast of North America. Second, it's not a moss; mosses are plants, and Ramalina is a lichen. Third, there is a true flowering plant (a bromeliad, actually, not a moss at all) with the common name Spanish moss that lives as an epiphyte in the warm humid southeastern U.S. as well as other tropical areas; clearly, this is not the same organism as R. menziesii, although the two may share superficial similarities such as overall growth form and color. If R. menziesii requires a common name for people to understand what it is, then let that name be something descriptive and biologically accurate, such as "lace lichen"; I've seen this name on a few websites and like it.
Lichens and fungi comprise a large part of my body of ignorance regarding the natural history of California. I find them very interesting but inscrutable, and they don't speak to me as loudly as do my beloved marine invertebrates. What this means is that I have a lot of learning to do, and this is always a Good Thing.