Of all the marvelous species of fungi on earth, the lichens are perhaps the most fascinating of all. Several hundred million years ago, a most remarkable marriage took place between the vast kingdoms of algae and fungi. Although these diverse kingdoms have survived more than a billion years of evolution, their union into a symbiotic life form called "lichen" enabled them to colonize practically every conceivable habitat on earth. Throughout rain-soaked forests of the world lichens hang in festoons from the tall branches, clothe the trunks and limbs in shrouds of green and gray, and carpet the ground in colorful shades of yellow, orange and red. Lichens flourish under the most extreme conditions, from windswept alpine peaks and frozen Arctic tundra, to sunbaked desert boulders and wave-battered rocky seashores. Lichens have also made themselves at home throughout our urbanized environment, including fence posts and roofing shingles, metal and painted surfaces, concrete and masonry, tombstones and statues, stained glass windows, and on the President's faces at Mount Rushmore National Memorial. But in spite of their amazing tenacity, many lichens are extremely sensitive to atmospheric pollution--a serious human blight that may lead to their extinction in the wild.

It wasn't until 1867 that the dual symbiotic nature of lichens was described by the Swiss botanist Simon Schwendener. Schwendener's hypothesis resulted in a bitter controversy among his colleagues who considered the green cells within lichens to be reproductive bodies of the fungus called gonidia. Free-living algae which resembled the green cells were considered to be gonidia which had escaped from the lichen thallus. Writing in Volume 13 of Popular Science Review (1874), the prominent English botanist J.M. Crombie referred to Schwendener's hypothesis as an "unnatural union between a captive Algal damsel and a tyrant Fungal master." Beatrix Potter, an excellent naturalist, writer and scientific illustrator of her time, wrote a paper on lichens in 1896. It included meticulous drawings to document her microscopic observations of fungal filaments intertwined with algal cells. Although never officially published, the paper was read at a meeting of the Linnaean Society on April 1, 1897. [Historical Note: Women were not admitted as Fellows (or members) of the Society until 1905.] Later, Beatrix Potter turned her attention to writing the "Tales of Peter Rabbit" and numerous other stories--much to the delight of children everywhere.