MUSHROOM GROWING 



are some of the heaths, notably Calluna and 

 Erica. Wherever Calluna and Erica are 

 found, truffles may not be anticipated. In- 

 deed, everything goes to show that the 

 truffles are distinctly calcareous plants and 

 are sharply limited in their distribution by 

 the presence of clay — seldom trespassing 

 upon sand. In this regard they are even 

 more sensitive than the plant w^ith w^hose 

 roots they are ordinarily associated. In 

 France truffles are most abundant in the so- 

 called gariques of the Midi, in the causses 

 of the southwest, and in the cosses and 

 galluches of Poitou, as well also as in the 

 lauses of Dauphiny. They are most abun- 

 dant in the Jurassic formation, especially in 

 the Lias, the Oolithes, and the Neocomian. 

 In this latter formation, the great truffle 

 field of Mont Ventoux occurs. Indeed, up 

 to a height of 800 meters this is practically 

 one continuous truffiere. 



It is difficult to explain why the European 

 truffles are not found in some quantity in 

 portions of Algeria, where the climate is 



202 



