6o 



PLECTOMYCETES 



[CH. 



themselves multiply by budding. Under appropriate conditions the mycelium 

 also bears naked, four-spored asci, the development of which has been 

 studied by Guilliermond. 



In Endomyces Magnnsii vegetative multiplication is by the separation 

 of oidia cut off by transverse walls. The ascus is the product of a definite 

 sexual process in which an elongated, swollen cell and a relatively narrow 

 one grow up, bend towards one another and unite. The single nucleus of 

 the smaller cell passes into the larger and fuses with its nucleus. Two karyo- 

 kinetic divisions take place, so that four nuclei and ultimately four spores 

 are produced (fig. 20). Fusion appears to take place indifferently between 

 unrelated or closely related filaments and parthenogenesis is not uncommon. 



In E.fibuliger, about half the asci result from the union of two filaments 

 while the remainder are parthenogenetic. The fusing hyphae are in most 

 cases closely related, often appearing as protuberances on each side of a 

 septum. They are similar at the time of fusion, but afterwards the growth 

 of one ceases, while the other swells to form the ascus. Besides producing 

 asci E. fibuliger multiplies rapidly by means of yeast-like conidia, which 

 closely resemble the cells of species of Saccharomycos (fig. 21). 



Fig. 21. Endomyccs fibuligtr Lind- Fig;. 12. Dipodascus albidus Lagerh.; fusion of Con- 



ner; formation of conidia; after jugating cells and nuclei ; after Dangeard. 



Guilliermond. 



VVolkia decolorans, the only known species of the genus Wolkia, has a 

 strono- mycelium, growing luxuriantly at a temperature of about 26°C; in the 

 immature state the mycelium is light pink, later globular red bodies appear. 

 These are the asci and are formed at the ends of single hyphae without 

 preliminary fusion. At first they contain dense cytoplasm and a large vacuole ; 

 later they become filled with blackish ascospores from two to fifteen in 

 number; in old cultures the spores are sometimes septate. 



