A TALEQF TRUFFLES 
     
    
   
   
    
     BY KATHERINE CLOUGH 
     
    
   
   
    
     Surprise is the most frequent reaction to the talk of truffles 
     
     in North America. They are thought of as exotic fungi growing only in 
     
     parts of Europe. But they do grow in North America. Dr. Jim Trappe of 
     
     the USDA Forest Service in Oregon estimates that the Pacific Coast 
     
     region of the U.S.A. and Canada harbours more truffles than any com- 
     
     parable area on earth. Most of these truffles have never been tasted; 
     
     of those that have, some have a fine flavour. The fact remains that 
     
     they are hard to find. 
     
    

    
     Truffles are underground fungi, some of which have long been 
     
     known for their culinary value. The black or Perigord truffle and the 
     
     white Italian truffle are highly prized by gourmets and fetch astro- 
     
     nomical prices at food markets. Both of these are referred to by tax— 
     
     onomists as true truffles. They are close relatives of the above 
     
     ground cup fungi. The majority of underground fungi are related to 
     
     the above ground gilled mushrooms and are often called false truffles. 
     
     This distinction gives no clue as to the edibility or flavour of the 
     
     truffle - edible species are found in both groups. To the casual ob- 
     
     server they all look very much the same, like a small wrinkled or 
     
     warty potato. Telling the species apart requires a lot of experience 
     
     since the main distinguishing feature is the way the spores are pro- 
     
     duced inside the truffle. To determine this requires a microscopic 
     
     examination. 
     
    

    
     Like mushrooms, truffles are ephemeral fruiting bodies which 
     
     produce spores to perpetuate themselves. The dispersal of spores can 
     
     only take place above ground. This is where we find the ecological 
     
     value of the pungent odour of ripening truffles. 
     
    

    
     As the truffle ripens, it develops an odour which intensifies 
     
     and attracts truffle flies. These flies burrow into the ground and 
     
     lay their eggs in the truffle. The larvae hatch and feed on the mat- 
     
     uring truffle. Eventually the adults emerge, carrying spores on their 
     
     bodies. 
     
    

    
     Small mammals are also important agents of dispersal. They dig up 
     
     truffles for food and the spores can be passed unharmed through their 
     
     digestive tracts and thereby dispersed throughout the forest. Truffle 
     
     spores have been found in the feces of many small mammals. Trappe re- 
     
     counts a story of how this fact helped to solve a mystery of mammalian 
     
     biology in Oregon. Scientists were puzzled to find the remnants of 
     
     flying squirrels in the digestive tracts of bobcats and coyotes. These 
     
     animals do not climb well enough to catch flying squirrels and the 
     
     squirrels are always seen high in the trees. However analysis of the 
     
     squirrel feces revealed the presence of truffle spores. It appears 
     
     that the squirrels do descend to the ground if they detect the odour 
     
     of a truffle. This puts them at the mercy of these predators . 
     
    

    
     Truffles are formed almost exclusively by mycorrhizal fungi. 
     
     These are the fungi that live in association with the roots of trees. 
     
     Both the fungus and the tree benefit from the association. The tree 
     
     receives minerals and some protection from the fungus, which in turn 
     
     receives carbohydrates from the tree.