Several years ago I saw a pictorial essay in a Sunday paper. The article described a drive down beautiful Highway 1 from San Francisco to Monterey. The first photo showed numerous wildflowers and was captioned “Queen Anne’s Lace Graces the Highway.” The flowers in question were actually Cow Parsnips. The second photo said “Sea Lions Rest Peacefully on the Rocks.” They were Harbor Seals. The final photo was entitled, “Spanish Moss Hangs from Windswept Trees.” It was not Spanish moss but a lichen called Old Man’s Beard. They were batting 0 for 3 in the photo department. I didn’t read the article.
Real Spanish Moss is found only in the southern United States – along the Gulf Coast, in Georgia and in Florida. It is not moss, and it sure isn’t Spanish. It is a bromeliad, a member of the pineapple family. Evolutionarily-speaking it is a highly evolved plant with true roots, stems and flowers. Spanish Moss is an epiphyte (meaning on plant) not a parasite; it receives all of its nutrients from rainwater.
Old Man’s Beard on the other hand is a lichen, and lichens are found all over the world. They can tolerate extremely harsh conditions. Some have been found in Antarctica living inside rocks! Considered pioneer plants, lichens are often the first living things to colonize new surfaces. By secreting acids, lichens break down rocks and help convert them to soil. And like Spanish Moss, they receive all of their nutrients from rainwater or fog.
A lichen is not a plant. It actually consists of two primitive plants. One is a fungus and the other an algae. The mnemonic device is “Alice Algae took a Lichen to Freddie Fungus and now they live together in a natural relationship.” Cute.
In cross-section, a lichen consists of an outer
protective layer, a photosynthetic layer (individual cells of algae surrounded by fungus), a storage area (for minerals and water), and a lower cortex (that provides attachment).
Botanists used to believe that the relationship was a mutual one – both partners benefited equally. The algae contributed sugars, nitrogen and other nutrients to the fungus. The fungus in return provided the algae a swell place to live with abundant water, minerals and protection.
Now many scientists believe that the fungus is actually parasitizing the algae. The algae can five just fine without the fungus, but the fungus needs the algae in order to survive. Not quite the idyllic relationship once postulated.
Most lichens reproduce by soredia, microscopic bodies consisting of tiny algae cells surrounded by fungus. These are formed in special fruiting bodies and then released. Wind, water or even animals transport these miniature lichens to new locations.
Scraping lichens off the walls is one job the maintenance workers at the Transamerica Building do not have. In urban areas, lichens usually do not grow because of their sensitivity to air pollution. They are especially susceptible to sulfur dioxide and nitric oxide, two common byproducts of internal combustion, engines. If you have lichens growing near your house, consider yourself fortunate; you breathe clean air.
After the Chernobyl nuclear accident large areas of northern Europe were exposed to radioactive malarial. Reindeer moss, which is actually lichen not moss, incorporated this fallout into its tissues. The reindeer feed almost exclusively on these lichens. Their flesh has become contaminated; it can not be eaten or sold. The Laplanders who had depended upon the reindeer for centuries suddenly found themselves out of a lifestyle. Because lichens are so slow growing, it may be another 50 years before the reindeer meat can be eaten again. Let’s not have any more nuclear accidents.