viii PREFACE 



exchange chromosomes, so that the daughter nuclei at the poles 

 remote from the (.46) nucleus have the constitution (AB)-\-(ab) 

 and the daughter nuclei at the poles near to the (^46) nucleus have 

 the constitution {Ab)-\-{aB). The (aB) nucleus which has thus come 

 into existence thereupon begins to diploidise the (Ab) mycelium. 

 This theory, as Quintanilha has pointed out, would serve to explain 

 not only the phenomenon observed by myself but also an allied 

 phenomenon observed by Brunswik. However, it does not seem 

 to be so simple as the theory of Rawitscher, nor does it account 

 for the " patchiness " of the diploid mycelium resulting from 

 illegitimate diploidisation. 



Part I of this volume treats of the structure and physiology of the 

 mycelium of the Higher Fungi, and it may therefore be considered 

 as a continuation of Part II of Volume IV. 



The first Chapter of Part I is devoted to the manner in which 

 hyphal fusions are made. Four types of hyphal fusions have been 

 recognised, and an appropriate terminology for them has been 

 introduced. New light has been thrown upon the mode of formation 

 of clamp-connexions. 



The second Chapter of Part I is concerned with the translocation 

 of protoplasm through the septate mycelium of certain Pyreno- 

 mycetes, Discomycetes, and Hymenomycetes and, in addition, it 

 contains a number of new observations on protoplasmic streaming 

 in the Mucorineae. The existence of a central pore in each septum 

 of the mycelium of an Ascomycete, a Basidiomycete, or a Fungus 

 Imperfectus was established by Wahrlich in 1893, but his work has 

 been very generally overlooked or forgotten. On this account a 

 number of his illustrations showing pores in septa have been repro- 

 duced. The author has been able to convince himself that in many 

 of the Higher Fungi the pore in each cross-wall is open and that 

 protoplasm flows freely through it from cell to cell. The formation 

 of pore-plugs and the healing of wounds in a mycelium have been 

 described and illustrated. 



Part II is devoted to studies in the mode of reproduction of 

 certain non-hymenomycetous Basidiomycetes, namely, Sporobolo- 

 myces, Tilletia, and Sphaerobolus. 



The first Chapter of Part II treats of Sporobolomyces roseus and, 



