THE FUNGI: ASCOMYCETES AND BASIDIOMYCETES 251 



become swollen and bud out numerous small processes, the sterigmata, 

 from each of which conidiospores are produced in chains in acropetal 

 succession. The spores are distributed by air currents, and on coming to 

 rest on a suitable substratum each germinates to produce a hypha from which 

 a fresh mycelium develops. 



Sexual Reproduction 



The archicarp or fruit primordium consists of three parts : a multicellular 

 stalk, an elongated unicellular ascogonium, and a unicellular trichogyne 

 (Fig. 242). The antheridium arises from the same initial hypha as the 



B 



STERILE 

 HYPHAE 



ASCOGENOUS 

 HYPHAE 



Fig. 242. — Aspergillus herharionim. A to D, Stages in the development of the 

 perithecium around the sex organs. E, Section through perithecium showing 

 ascogenous hyphae. F, A single ascus containing ascospores. {After de Bary.) 



ascogonium, or from an adjacent one. It is unicellular and multinucleate. 

 Fusion takes place between the antheridium and the trichogyne, which 

 become twisted around one another during the process. It has not been 

 proved, however, that the antheridium is ever functional in fertilization. 

 In some species the antheridium may be absent, but this does not prevent 

 the further development of the ascogonium. In either case the ascogonium 

 becomes divided into a number of binucleate cells, from each of which a 

 septate ascogenous hypha is given off. From the terminal cell of each 

 hypha or from the cell below, termed the penuhimate cell, an ascus is 

 formed by elongation. In this cell the two nuclei fuse together. 



Shortly after the development of the sex organs, hyphae begin to grow 



