386 FIRST FORMS OF VEGETATION. 
occasionally occurring in woods in autumn. The 
stem is from three to five inches high, snowy- 
white, irregular, hollow, deeply furrowed, often 
full of holes or sinuses like the fluted trunk of 
the yarroura or paddle-wood of the Indians. The 
cap is deflexed, and commonly divided into curled 
or folded lobes which adhere to the stem, but 
it is extremely irregular and variable, and 
has neither gills nor pores. Its substance is 
extremely brittle, the surface being soft like 
satin. 
The most valuable, however, of all the esculent 
fungi is oe the truffle (Zuber cibarium, Fig. 
42). This curious sub- 
terranean puff-ball, for 
such it is, is so local and 
scarce that it is very 
little known’ except 
amongst wealthy and 
titled families in this 
Fic. 42.—TuBER CIBARIUM. country, seldom appear- 
ing at common tables; and probably the greater 
part of what is sold is imported. It is very rare 
in Scotland, but by no means uncommon in some 
parts of England, especially where a limestone 
soil prevails. It is usually found in beech-woods 
and oak plantations growing in clusters or in a 
sort of semicircle in the same way as mushrooms, 
