214 THE ASCOMYCETES 



occurring in England; and Gilkey (1916), 37 species in California. 

 In a later monograph Gilkey (1939) lists and describes 58 species, 

 included in 19 genera, as occurring in North America. All are 

 edible, some species being highly prized as food, especially Tuber 

 aestivimi, T. brwnale, T. inelaiiosponnn, T. viagnatimi, and T. 

 7iitidum. Although the number of known species of truffles is 

 not large, edible ones may occur so abundantly as to make their 

 collection commercially profitable. Persons who collect truffles 

 commercially, especially in France and Italy, work with the help 

 of trained dos^s or hogs that locate the truffles by scent. 



Reproduction. No asexual or conidial stage is known to oc- 

 cur anions^ Tuberales, with the possible exception of one species 

 of Tuber found to form conidia in culture. Their only known 

 reproductiye stage is ascospores. Unfortunately the early devel- 

 opm.ent of ascocarps, has not been obseryed; hence little is known 

 about their sexuality. Dangeard (1894) found that crosiers are 

 formed in T. bnniiale and T. dryophihnn and that the customary 

 number of free nuclei is produced within each ascus. The num- 

 ber of ascospores, howeyer, yaries from 1 to 8 per ascus, and the 

 wall of the ascospores at maturity is ornamented with spines, 

 warts, or reticulations. Ascospore dispersal is accomplished only 

 after decay of the rind or through the agency of animals, 

 especially rodents, that utilize truffles for food. 



Classification and relationship. The truffles are divided into 

 two families: Eutuberaceae, with hymenial chambers that open 

 to the outside, and Balsamiaceae, with closed chambers. It re- 

 mains questionable whether this basis is adequate for separation. 

 Evidence presented by Bucholtz (1897) shows that Tuber exca- 

 vatinn, typifying the Eutuberaceae, is at first gymnocarpous. In 

 Genea, too, the ascocarps are initially closed, and they open 

 apothecium-like at maturitv^ These observations incline some 

 mycologists to regard the Tuberales as discomycetous. The find- 

 ings of Bucholtz (1903, 1910) indicate that the convolutions 

 which are to become the hymenium arise as invasrinations from 

 the upper surface of the ascocarp. Bucholtz (1910) regards the 

 Balsamiaceae as intermediate between Pezizales and Helvellales. 



On further study, as has been indicated, certain of the species 

 formerly placed among the Elaphomycetaceae and Terfeziaceae 

 have been found to belong among the Tuberales. Relationships 



