i84 RESEARCHES ON FUNGI 



new hyphal fusions being established to repair the damage done by 

 the loss of old ones. 



(5) Social organisation. As we have seen in previous pages, 

 hyphal fusions enable many myceha of the same species occupying 

 the same substratum to unite together to form a single compound 

 mycelium which acts as a social unit in the production of fruit- 

 bodies and spores. One only of the components of the compoujid 

 mycelium may give rise to a fruit-body, in which case all the other 

 components remain sterile but contribute to the reproduction of 

 the species by yielding up their contents to the developing fruit-body. 



Sex and Hyphal Fusions in the Hymenomycetes. — With a 

 view to throwing further hght on the relation between hyphal 

 fusions and sexual phenomena in the Hymenomycetes, some 

 additional remarks will now be made. 



In certain heterothallic species, e.g. Coprinus radians ( = C. 

 domesticus) and C. Rostrupianus , the spores and the monosporous 

 mycelia are of two sexual kinds which may be represented by the 

 symbols {A) and (a). When a haploid mycelium {A) unites with 

 a haploid mycelium (a), a diploid mycehum is formed which we 

 may represent by the symbols (^) + (a), so that, in each of the 

 species under consideration, from the sexual point of view there 

 are three possible kinds of myceha : (A), {a), and (^)+(a). With 

 two sets of mycelia 



{A), (a), {A)+{a), 

 {A'),{a')AA')+{a'), 



there are fifteen possible combinations taken two at a time : 



{A) X (a), {A) X (v4)+(a), {a) x {A) + {a), 



{A') x (a'), (^') X {A')+{a'), (a') X {A') + {a'), 



{A) X {A'), {a) X (a'), (A) x («')> («) X {A'), 



(A) X (^')+(a'),(a) X {A')Ma'),{A') X {A) + {a),{a') X {A) + {a), 



{A) + {a) X {A')+{a'). 



From analogous observations made on C. lagopus there is every 

 reason to believe that the two mycelia in every one of the fifteen 

 combinations would fuse hyphally with each other, were they given 

 the chance. In general, we may assume that, in a species having 

 two sexual kinds of spores, any one kind of mycelium at one and 



