SUBTERRANEAN FUNGI— TUBERACEAE 191 



that the individuals attain a far larger size and a greater 

 value, from the utilitarian point of view. The interior does 

 not become pulverulent in the genuine Truffles, although it does 

 in Elaj^hoviyces, and when cut through in section the flesh is 

 mottled and veined. Slices of the substance under the micro- 

 scope exhibit rounded delicate sacs or asci, which enclose the 

 sporidia lying freely within them. Externally the surface of 

 the peridium is often warted or rough, and the resemblance to 

 a subterranean Scleroderma is more remote. The total number 

 of described species scarcely exceeds one hundred and twenty, 

 of which fifty belong to the genus Titber, and all except eiglit 

 are European. Of the extra-European species two belong to 

 Ceylon,^ one to Malacca, one uo North America, three to South 

 America, and one to Tasmania. It is somewhat remarkable 

 that North America is so deficient in examples of this group, as 

 only two or three of the European species have been found there 

 in addition to the one indigenous species. The species 0^ My- 

 litta, or native bread, are not genuine members of this group, • 

 although often associated with them, but they would seem to 

 belong rather to that congeries of imperfect forms termed 

 SdcTotia. 



The most prolific country for the production of species of 

 Truffles is Italy, but the most celebrated of Truffles for the 

 table are those of France. At one time Truffle hunting was 

 conducted with success in the southern coun- 

 ties of England, but for many years the industry 

 has declined, and is now almost extinguished. 

 This is said to be due to the importation of 

 French Truffles of more exquisite flavour, and 

 at a lower price. All Truffle spores are large, fig. 79. — Aiveo- 

 those of our common British species being late sporidium of 



Truffle. 



alveolate, or covered with hexagonal pits, the 

 walls of which are of transparent membrane (Fig. 79). The 

 spores of the French Truffles are spinulose (Fig. 80). It is easy, 

 by aid of the microscope, to determine even by a fragment the 

 French from the English Truffle, or Tuber aestivum from Tuber 

 melanosporum, on account of the difference in the sporidia. " The 

 extent of the trade in Truffles may be estimated from the fact 

 ^ Some kind of Truffles are reported to be found in the Kangra Valley, India. 



