448 



BOTANY 



PART II 



thickened epispore. They are set free iu the soil by the breaking down of the asci 

 and of the wall of the fructification. 



The fructifications of many of the Tuberaceae are edible ( 70 ), and have an aromatic 

 odour and taste. They are, for the most part, obtained from France and Italy. 





FIG. 393. Tuber rufum. 1, A fructification in vertical section ( x 5) ; a, the cortex ; d, air-containing 

 tissue ; c, dark veins of compact hyphae ; h, ascogenons tissue. 2, A portion of the hymenium 

 (x 460). (After TULASNE, from v. TAVEL. Pihe.) 



Of the edible varieties, the most important are the so-called black truffles 

 belonging to the genus Tuber, viz. Tuber brumale, melanosporum (Perigord Truffle), 

 aestivum, mesentericum. The fructifications of these species have a warty cortex of 

 a black, reddish-brown, or dark brown colour. The white truffle, Choiromyces 

 meandriformis, the external surface of which is pale brown, is also edible. 



The fructifications when very young are open as in the Discomycetes. The 

 Truffles seem most nearly related to the Helvellaceae. 



