358 



COMPARATIVE MORPHOLOGY OF FUNGI 



and may sink from eight to four to two to one, with proportional increases 

 in size. The spores generally become multinucleate while still inside the 

 ascus. The entire morphological and biological development of the 

 asci which we could follow from the Plectascales to Pezizales, their 

 biological discharge apparatus, their transition from spherical to clavate 



Fig. 240. — Tuber rufum. 1. Section of fructification. 2. Portion of interior of fructi- 

 fication, a, rind; c, venae internae (trama plates) ; d, venae externae; h, hymenium. {After 

 Tulasne.) 



form and their arrangement in regular hymenia, has degenerated in the 

 Tuberales on account of their endogenous formation; they have lost 

 their function of spore dissemination, apparently also their clavate form 

 and arrangement in hymenia. The striking correspondence between 

 Tuber and the Plectascales is, according to this concept, only a conver- 

 gence phenomenon. 



