388 FIRST FORMS OF VEGETATION. 
very fond of them, and advantage is taken of their 
instinctive knowledge of the spots where they are 
found, and their natural propensity to dig them 
up, to gather a more plentiful supply than could 
be obtained by a chance search. Nees von Essen- 
beck relates an instance of a poor crippled boy 
who could detect the hiding-places of truffles with 
more certainty even than the best dogs, and thus 
earned a comfortable livelihood. In some parts 
of France, truffles are detected by observing a 
species of fly which alights on the ground above 
the spots where they grow. They have been 
successfully cultivated by Bornholz. They are 
found in dry and light calcareous soil in woods 
throughout the whole of Europe, as well as in 
Japan, India, Africa, and New Zealand. In the 
warmer parts of Europe, which is the most prolific 
region of truffles, all that is needed to procure a 
constant supply is simply to sow a few acorns in an 
enclosed spot on the calcareous downs. As soon 
as the young oaks have grown a few feet in height 
the truffles appear, and a harvest is obtained for 
many years successively without further trouble. 
There are forty distinct species in Great Britain ; 
and France and Italy possess double that number. 
Very few of these, however, are used as articles of 
food or condiments. Though some species have 
dark and sombre hues, there are many others that 
