42 RESEARCHES ON FUNGI 



repeats the process of ascus-cell formation already described. It 

 is evident that the formation of hooks is an important 

 factor in arranging the asci in an advantageous manner in the 

 hymenium. 



Gaumann, 1 in his discussion of the phylogeny of the Hymeno- 

 mycetes, says " clamp formations would be incomprehensible if one 

 could not explain them as a relic of the Ascomycetes." On the 

 other hand, it seems to me not impossible that the hooks of the 

 ascogenous hyphae of the Discomycetes and the clamp-connexions 

 of the diploid mycelium of the Hymenomycetes may, in response 

 to two quite different physiological needs, have originated inde- 

 pendently of one another. 



In attempting to homologise the hooks of Pyronema conjluens 

 and other Discomycetes with the clamp-connexions of Hymeno- 

 mycetes, Mile Bensaude, Kniep, and Gaumann have chosen as 

 examples of clamp-connexions those which, in some species of 

 Hymenomycetes, are to be found at the base of the basidia and not 

 those which occur in the diploid mycelium and in the general tissues 

 of the fruit-bodies. It is true that, in the formation of a hook of 

 an ascogenous hypha and of a clamp- connexion at the base of a 

 basidium, conjugate nuclear division and the fusion of two uninu- 

 cleate cells take place, but there the analogy ceases ; for ( 1 ) a basidium 

 arises from the ultimate cell of an erect hypha, whereas an ascus 

 arises from the penultimate cell of a semicircularly bent hypha ; and 

 (2) the hypha which forms the clamp-connexion at the base of a 

 basidium is a special lateral hypha, whereas the cell which in the 

 hook of an ascogenous hypha forms the structure which is supposed 

 by Mile Bensaude, Kniep, and Gaumann to correspond with a clamp- 

 connexion at the base of a basidium is the terminal cell of the 

 ascogenous hypha. 2 These differences in detail in the mode of 

 formation of the hooks in Discomycetes and of the clamp-connexions 

 at the base of the basidia of Hymenomycetes appear to me to greatly 



1 E. Gaumann, he. cit., p. 4U0 ; also E. Gaumann and C. W. Dodge, Comparative 

 Morphology of Fungi, New York, 1928, p. 421. 



2 These morphological dissimilarities have previously been noted, among others 

 by M. and Mme Moreau {Rev. gen. de Bot., T. XXXVII, 1925, pp. 470-471) and by 

 H. C. I. G wynne -Vaughan and B. Barnes, Structure and Development of the Fungi, 

 Cambridge, 1927. p. 133. 



