A TKUFFLE-HUNTER 229 



The sand is methodically removed in vertical slices 

 At the bottom of each burrow is a Bolboceras engaged 

 in eating its truffle. 



Let us repeat the experiment with the partly eaten 

 fungi. The result is the same. In one short night the 

 food is divined under its covering of sand and attained 

 by means of a burrow which descends as straight as a 

 plumb-line to the point where the fungus lies. There 

 has been no hesitation, no trial excavations which have 

 nearly discovered the object of search. This is proved 

 by the surface of the soil, which is everywhere just as 

 I left it when smoothing it down. The insect could 

 not make more directly for the objective if guided by 

 the sense of sight ; it digs always at the foot of the 

 straw, my private sign. The trulfle-dog, sniffing the 

 ground in search of truffles, hardly attains this degree 

 of precision. 



Does the Hydnocystis possess a very keen odour, 



such as we should expect to give an unmistakable 



warning to the senses of the consumer ? By no means. 



To our own sense of smell it is a neutral sort of object, 



with no appreciable scent whatever. A little pebble 



taken from the soil would affect our senses quite as 



strongly with its vague savour of fresh earth. As a 



finder of underground fungi the Bolboceras is the rival 



of the dog. It would be the superior of the dog if it 



could generalise ; it is, however, a rigid specialist, 



recognising nothing but the Hydnocystis. No other 



fungus, to my knowledge, either attracts it or induces 



it to dig.» 



' Since these lines were written I have found it consuming om 

 of the true tuberaceae, the Tuber Requenii, TuL, of the size oi a 

 cherry. 



