Contents

07 August 1992
Vol 257, Issue 5071

About The Cover

American chestnut trees in the Great Smoky Mountains, North Carolina, before a blight epidemic that destroyed several billion mature trees when the Asian fungus Cryphonectria parasitica was unintentionally introduced early this century. The cloning of an endogenous virus that infects the fungus provides the potential for effective biological control of chestnut blight and the restoration of this once valuable forest tree. See page 800. [Photograph: Museum of North Idaho]