The dark gray color of Stone Mountain is not the granite, but the lichens which grow on practically all the weathered stone. Behaving like booby traps, these pioneer plants have tricked a number of venturesome climbers to their deaths. In a rain they absorb water and become quite slippery, almost as if the stone were coated with grease. In dry weather they crumble underfoot and the tiny particles roll like shot to start a hiker sliding. Walking on almost level ground can become an adventure. The lichens are a pioneer plant form, a symbiotic relationship of fungi and algae. A fungus, unable to manufacture carbohydrates when alone, must live as a parasite on another plant. An alga can manufacture sugar or starch, provided it is kept moist and has the necessary ingredients. Working as partners, the fungi absorb and hold moisture and dissolve some essential chemicals from the rock; the algae mix these and cook with the sun’s energy to make food for the partnership. Their assault is the first step in reducing stone to soil. In this duty they are followed by grasses, weeds, shrubs and finally trees. There are three growth types of fungi: crustose, which appears as thin crusts on the rocks, and is the most prevalent at Stone Mountain; foliose, which has leaflike body and draws almost recognizable pictures; and fruticose, which stands up in mossy little clumps. [Illustration: Two young explorers beside a rain pit at the top, where fairy shrimp and the rare _Amphianthus pusillus_ live.] [Illustration: {uncaptioned}] Stone Mountain has a rare genus of the crustose, the _Pyrenopsis phaecocca_ which is found only in Georgia, on the granite outcrops of the Piedmont section from Atlanta to Augusta. Another crustose variety is a dull, dark red and grows in splotches, so it looks as if a boy with a wide brush had been smearing the boulders with barn paint. Some of Stone Mountain’s fruticose lichens stand up like little powder puffs an inch or two tall, and are comparative to the extensive reindeer moss of Alaska’s tundras. In a long drought many of the little clumps break off and go blowing about the mountainside like miniature tumbleweeds. Veteran quarrymen have noted that it takes about 25 years for a freshly broken piece of granite to weather sufficiently for lichens to grow. Most spectacular of all Stone Mountain’s plant life are the trees. Gnarled and twisted red cedars, almost a foot in diameter, cling desperately to narrow cracks in the deep slopes. Some are estimated at 500 to 800 years old, and they look every bit of their age. Pines, stooped and bent by mountain winds and stunted by long summer droughts, poke their roots into rock crevices and strain mightily to widen the slits. Some of these may be 150 years old. On the other hand, a giant loblolly growing in the rich red loam at the foot of the mountain, near the grist mill, measured nine feet in circumference, and had only 90 growth rings.