IV] 



TUBERALES 



135 



TUBERALES 



The Tuberales are typically subterranean though some species are only 

 imperfectly buried, or grow among decaying leaves. When mature the 

 fruits emit a powerful odour by which rodents are apprised of their where- 

 abouts. The ascocarp is eaten and the spores dispersed after passing through 

 the alimentary canal of the animal. 



The ascocarp is more or less globose, sometimes completely closed, 

 sometimes with a small opening. The hymenium may form a smooth lining 

 to the fruit or may be thrown into elaborate folds so that the fertile region 

 is divided into chambers. The asci contain one to eight spores, but, as far 

 as is known, eight nuclei are always produced. The epispore is often 

 elaborately ornamented at maturity. 



Early investigators classed the Tuberaceae with the hypogeal Gastero- 

 mycetes, and a consequence of this survives in the use of the term gleba to 

 describe the contents of the ascocarp, including both vegetative hyphae and 

 hymenium. 



The Tuberales include a single family, the Tuberaceae; their relationship 

 is probably to the Pezizaceae and Rhizinaceae. One or more series can be 

 traced between these families and the truffles, the principal modifications 

 being in the direction of adaptation to subterranean conditions by increased 

 protection of the hymenium. This appears to have been achieved either by 

 retaining the closed form of the young pezizaceous apothecium {Genea, 

 PacJiyphloeus) or by invagination of the fertile layer {Tuber) over a widely 

 exposed surface such as is found in Rhisina or Sphaerosoina. In either 

 case room has been made for 

 additional asci by throwing the 

 hymenium into elaborate folds. 

 Massee, however, regards the 

 globose asci and dark-coloured 

 sculptured spores of Tuber as 

 primitive, and derives from it 

 Genea, and thence the Pezi- 

 zales. 



Tuberaceae 



In Hydnocystis and Genea 

 the ascocarp is fleshy or warted; 

 it has a single aperture often 

 more or less closed by project- 

 ing hyphae. Internally the 



hymenium may form a smooth ^'g- 94-. a- Genea KlotzschU B. and Br.; ascus and para- 

 T • ■ n ■ ' physis ; b. Genea hispidula Vitt. ; apothecium; i. 



immg, or, m i^enea, is more C^wa i//5«eraa Vitt.; apothecium; after Massee. 



