256 COMPARATIVE MORPHOLOGY OF FUNGI 



sterile parts. In the saprophytic group, the high point is reached by 

 Ascopolyporus and its relatives which are equivalent to the higher Poly- 

 porales; in the parasitic species, the high point is reached by the Claviceps 

 group which, through an extensive biological differentiation of its sterile 

 (i.e., the parts forming imperfect forms) and of its fertile parts, attains 

 to types which are unique among fungi. In many lower forms, as Nectria 

 and Corallomyces, the conidia and perithecia arise successively on the 

 same stromata while in the higher forms the conidial and perithecial 

 stromata are developed separately (e.g., Isaria-Cordyceps group) and 

 in part also differ biologically (Sphacelia-Claviceps). 



As all these fructifications of the perfect stage are to a certain degree 

 compound fructifications, it is not surprising that the original solitary 

 perithecia which have secondarily collected to an aggregate fructification 

 (stroma) gradually merge their individuality in this stroma. While 

 they originally were formed with a well-developed wall on or in the stro- 

 mata, in the immersed forms this wall is no longer a protection and 

 gradually degenerates, and the perithecia are no longer differentiated 

 from the ground tissue but as schizogenous cavities in the periphery of 

 the stromata. 



The sexual organs of the Hypocreales are connected to those of the 

 Plectascales and Perisporiales. In the former, the antheridium, which is 

 still present in some of the lower forms and possibly still functional, is 

 rapidly lost and the ascogonium develops alone. Caryogamy is not 

 entirely suppressed, but, instead of cross fertilization, for the first time in 

 the fungi under discussion, parthenogamy occurs between two cells of 

 the ascogonium. Thus begins a series of deuterogamous forms which will 

 occupy us until we finish the fungi. 



