viii PREFACE 



In the second and final chapter of Part II it is shown in detail 

 that, in Coprinus lagopus, a diploid mycelium is able to diploidise 

 an appropriate haploid mycelium. This discovery seems to provide 

 a clue for the solution of the problem of the biological significance 

 of conjugate nuclei. Incidentally, in the course of the work, it 

 has been possible to calculate the speed of movement of nuclei 

 derived from one haploid mycelium or an appropriate diploid 

 mycehum along the hyphae of another haploid mycehum which 

 the first mycehum is diploidising. In discussing the phenomena 

 connected with the estabhshment of conjugate nuclei in myceha 

 which have been mated, it has been found convenient to employ 

 the terms diploidisation, the diploidisation process, to diploidise, etc., 

 first introduced by myself in an article recently pubhshed in Nature. 

 This volume contains one hundred and forty-nine illustrations 

 in the text, including eighty-eight drawings and sixty-one photo- 

 graphs. Fourteen of the drawings have been borrowed from other 

 authors. The other drawings were executed by my own hand or 

 in conjunction with Miss Ruth Macrae. For copying the drawings 

 reproduced in Figs. 85, 93, 94, and 95 my thanks are due to 

 Dr. Nellie Carter. The source of each borrowed illustration is 

 acknowledged in the text. 



Of the sixty-one photographs in the text fifty-one were made 

 under my direction, and the others were very kindly contributed 

 by friends and correspondents : four by the late G. F. Atkinson ; 

 two by C. A. Pemberton ; and one each by B. 0. Dodge, Somerville 

 Hastings, A. E. Peck, and the late J. E. Titley. 



At the end of the volume have been appended four Plates which 

 represent an attempt on the part of the author to visualise diagram- 

 matically, in the present state of our knowledge, successive stages 

 in the diploidisation (1) of one haploid mycelium by another haploid 

 mycelium and (2) of a haploid mycelium by a diploid mycehum. 



The researches recorded in this volume, together with other 

 researches still to be pubhshed, were made the basis of a series of 

 six lectures, called Recent Advances in our Knowledge of the Fungi, 

 delivered under the auspices of the Norman Wait Harris Foundation 

 in November, 1927, at Northwestern University, U.S.A. 



My best thanks are due to the Canadian National Research 



