7 2 RESEARCHES ON FUNGI 



was without effect on the phenomenon. However, when a thin 

 plate of glass or of mica was placed between the two mycelia in 

 such a way as to form a water-tight partition (cloison etanche), the 

 repulsive action was just as strong or nearly as strong as if the 

 mycelia had not been separated. On the other hand, a thin water- 

 tight partition of lead suppressed the repulsive action completely. 

 Vandendries and Brodie, as a result of these and other experiments, 

 have come to the following conclusions : (1) the repulsive action is 

 not of a chemical nature but is due to radiation ; (2) this radiation 

 is more or less arrested by partitions placed between the mycelia ; 

 and (3) the action of the partition is dependent on the substance of 

 which it is composed, its density, and its thickness. 



If the mutual repulsion of hyphae belonging to different haplonts 

 of Lenzites betulina, as observed by Vandendries and Brodie, is due 

 to radiation, it may well be that, in the fungi generally, the mutual 

 attraction shown by two hyphae about to fuse with one another is 

 also due to radiation. 



Passage of Nuclei through Hyphal Fusions. — We now know 

 that, in the Hymenomycetes and the Uredineae, when two haploid 

 mycelia of opposite sex fuse together, they subsequently diploidise 

 one another. We are therefore justified in inferring that, during 

 the diploidisation process, one or more nuclei of each mycelium pass 

 through the hyphal fusions into the other mycelium. 1 



To what extent, if any, in ordinary vegetative hyphal fusions 

 nuclei pass through the junction-places from one hypha to another 

 still remains to be determined by exact observation and experiment. 

 As will be shown in the next Chapter, great quantities of cytoplasm 

 often pass through hyphal bridges from one mycelium to another ; 

 but to what extent, if any, the streams of cytoplasm carry nuclei 

 with them is at present unknown. 



Brierley, 2 in discussing variation or subspecific grouping in fungi, 

 has taken into account the possibility of nuclei passing via hyphal 

 anastomoses from one strain of a fungus to another strain. 



1 Cf. these Researches, Vol. IV, 1931, Part II, Chapter II. 



2 W. B. Brierley, "Variation in Fungi and Bacteria," Proc. Internat. Cong. Plant 

 Sci. Ithaca, New York, Vol. II, 1929, pp. 1629-1654 ; also " Biological Races in Fungi 

 and their Significance in Evolution," Ann. App.Biol., Vol. XVIII, 1931, pp. 420-134. 



