PLEURAGE ANSERINA 



177 



that of the seven monosporous mycelia which have fused together, 

 one only is carrying on the work of reproduction at the expense of 

 the protoplasm of all the seven mycelia. Thus, six of the mono- 

 sporous mycelia, while themselves sterile, are assisting the seventh 

 in carrying out its reproduc- 

 tive function. 



Another Pyrenomycete in 

 which hyphal fusions may be 

 readily observed is Pleurage 

 anserina (Fig. 101) which 

 often comes up spontaneously 

 and fruits very freely upon 

 unsterilised horse-dung balls 

 in laboratory cultures at 

 Winnipeg. Miss Dowding.^ 

 working under my direction, 

 found that normally there are 

 four binucleate bisexual spores 

 in each ascus but that, occa- 

 sionally, a single normal spore 

 is replaced by two uninu- 

 cleate unisexual dwarf spores. 

 When a number of normal 

 spores or two dwarf spores 

 are sown together in a drop of 

 the culture medium, the my- 

 ceha which they produce soon 

 become united together in 

 many places, so as to form a single network. The union of two 

 mycelia derived from two dwarf spores is illustrated in Fig. 102. 



To those Discomycetes in which monosporous mycelia unite to 

 form a single compound mycelium may be added Ascoholus mag- 

 nificus, the very large fruit-bodies of which are illustrated in Fig. 103. 

 A number of ascospores of a fruit-body of this species were shot 



Fig. 101. — Pleurage anserina. On the steri- 

 lised horse dung in the glass dish is a 

 mycelium which originated from a single 

 normal ascospore. The mycelium is about 

 two weeks old and has fruited abun- 

 dantly. The perithecia are scattered 

 over the surface of the culture medium 

 and their black necks can be seen pro- 

 truding above the white myceliimi. The 

 asci usually contain four binucleate 

 bisexual spores but, occasionally, one of 

 these normal spores is replaced by two 

 dwarf spores each of which is uni- 

 nucleate and unisexual. Photographed 

 by A. H. R. BuUer and E. Silver Dow- 

 ding. Natural size. 



1 E. Silver Dowding, " The Sexuality of the Normal, Giant, and Dwarf 

 Spores of Pleurage anserina (Ces.) Kuntze," Annals of Botany, vol. xlv, January, 

 1931. 



VOL. IV. 



N 



