INTRODUCTION 19 



the environment and that in consequence fungi are to be found in every major 

 division of the plant kingdom ; though rare among mosses and ferns, they are 

 far from uncommon in the flowering plants. From this is derived the second 

 principle that the fungi do not constitute a natural group, and that all the 

 phyletic lines lead sooner or later to holophytic origins. Mycologists, like 

 lichenologists, are specialists and have been fond of thinking of the auton- 

 omy of the fungi as something inherent, and they have not infrequently 

 resorted to the most ingenious and specious arguments to support such 

 opinions. From the objective point of view, the autonomy of the fungi rests 

 on grounds no better than that of the lichens, and they were distributed 

 phyletically in the first edition (1909), a treatment long accorded the 

 hysterophytic flowering plants and more recently the lichens (Clements 

 1896, 1903). 



The third principle is that the ecological approach to the morphology 

 and development of the fungi constitutes the best attack upon their evolution 

 and phylogeny. This is primarily because of its inclusive character, nothing 

 that can affect the organism being left out of account, but largely also 

 because it focuses attention upon the three essential processes of spore pro- 

 duction, spore protection, and spore distribution. The claimsof cytology to be 

 the final arbiter of questions of origin and relationship among the fungi 

 have been much advanced of late, but this can only play a part rather than 

 assume the paramount role in this field. Quite apart from the fact that its 

 viewpoint is necessarily restricted is the further consideration that no other 

 approach is so beset with the bypaths of interpretation. The task of tracing 

 the phyletic development of the fungi is one to demand all the resources of 

 investigation, chief among which must be experiment on the largest and 

 broadest scale possible, in both field and laboratory. 



