146 COMPARATIVE MORPHOLOGY OF FUNGI 



In Eremascus fertilis, the division of the hyphal nucleus before copulation 

 is strongly reminiscent of Basidiobolns, in Endomyces Magnusii the 

 extrusion of the supernumerary nuclei is reminiscent of Endogone. Only 

 the zygote in Basidiobolus and Endogone develops to a hypnospore, while 

 in Eremascus fertilis and Endomyces Magnusii to a sporangium in which 

 are formed the ascospores which function as hypnospores. 



From these sexually well-developed forms, there may be observed 

 a gradual decline of sexuality. Thus in a second stage, Endomyces 

 fibuliger, the copulation branches can still copulate; however, they usually 

 develop parthenogenetically, so that the life cycle almost disappears 

 in the haploid phase; 



Mycelium— >-Gametangia— >Ascus— * Ascospores 

 Diagram XV. 



Nevertheless, in E. fibuliger sexuality is not entirely suppressed; it is 

 possible for two sprout cells to copulate; no special sexual organs are 

 used, but the sexual act is shifted into the thallus and takes place 

 pseudogamously : 



PC R 



Mycelium— >Sprout cells— ^Ascus— > Ascospores 



Diagram XVI. 



Finally, in the third and last stage, E. javanensis and E. capsularis, 

 the functionless gametangia are no longer formed; similarly, the sexual 

 act no longer takes place between two vegetative cells, and the thallus 

 mostly disappears in a sprout mycelium. Thus the life cycle is as follows : 



I 1 



Sprout mycelium— >Ascus— ► Ascospores 



Diagram XVII. 



Herewith morphologically we arrive at the stage of the yeasts. Before 

 we proceed to the discussion of this family, two more genera, Pericystis 

 and Ascoidea, should be briefly mentioned, which, although insufficiently 

 known, certainly belong in the vicinity of the Endomycetaceae. Peri- 

 cystis apis, the cause of chalk brood of bees, is a heterothallic form in 

 which the sexual dimorphism marks even the habit of the mycelium. A 

 multispored ascus is formed by copulation of two gametangia of unequal 

 size (Claussen, 1921). P. alvei (A.D. Betts, 1912) occurs on stored 

 pollen in beehives. 



Ascoidea rubescens forms a thick reddish-brown mass in the slime-flux 

 of beech. It is composed of felt-like tissue of ramose, septate hyphae, 



