ONCE, FOR A HEART-STOPPING moment, they thought they had found their desire. Rounding a bend, they came upon a cavern alive with color; towering vines and trees laden with great clusters of grapes; bushes aflower with myriads of gorgeous buds. Dorothy sprang forward with a cry of joy—but when she touched one of the mock roses it shattered to fine, white, powdery snow; upon investigation the trees, the vines and “grapes” turned out to be of the same, perishable nature. And Tim remembered their name. “Oulopholites,” he said. “Sulphate of magnesia and gypsum. Mother Nature does repeat herself, you see. She uses the same forms, but these are lifeless mimicry.” And he looked at his watch. “Guess we’d better turn back, eh, skipper? We’ve been two hours on the prowl, and there doesn’t seem to be