Introduction 



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THE development of systematic mycology during the past quarter of a 

 century has been characterized by three features of much significance. 

 The first of these has been the relative exhaustion of fields long-tilled 

 at home and the consequent tendency to shift the basis of criteria, with the 

 result that sections have been changed into genera and genera into families. 

 A second feature has been due to the increasing exploitation of the Tropics, 

 which has disclosed a large amount of novel material, in certain orders 

 especially. Of even greater interest and significance has been the work of 

 the "revisionists" in testing the foundations of the subject and in removing 

 or refashioning faulty units. The chief worker in the arduous task of revalu- 

 ating type specimens and other authentic material has been Hoehnel, but a 

 large part in this has also been taken by Bresadola, Theissen, Sydow, Petrak 

 and Weese, to mention only the most active. Essential as this has been to 

 the development of mycology, it was inevitable that it should reveal great 

 differences as to the facts and even greater ones of interpretation. 



In spite of the industry of this group, as well as of others, it is evident 

 that the application of scientific methods to the revision of the fungi is only 

 begun. This is clearly demonstrated by the frequent wide divergence in the 

 treatment of both genera and families, which may be illustrated by several 

 striking examples. Probably the most illuminating instance is afforded by 

 the so-called Pseudosphaeriaceae. The concept of a new family based upon a 

 sclerotioid perithecium with paraphysoids in place of paraphyses was first 

 advanced by Hoehnel (1907), who during the course of the next ten years 

 added several genera to the original two, chiefly by transfer from other 

 families. By 1918, Theissen and Sydow had expanded the group to more 

 than a score of genera and had reached the conclusion that "It has already 

 been shown with sufficient clearness that the Pseudosphaeriales are to be 

 regarded as an order containing several families, even though a conclusive 

 treatment is not yet possible" (Ann. Myc. 16:34 1918). In the same year, 

 Hoehnel spoke as follows of this expansion of the group: "To what lengths 

 the PseudospIuieriaceae-st3irch may be carried is shown by the following. 

 Parodiella caespitosa Winter is treated by Theissen and Sydow as a genuine 

 species of the genus, therefore as one of the Pseudosphaeriaceae. The 

 examination of the original specimen of this fungus in Rabenh. Wint., F. 

 europ. No. 3249 convinces me that this is a wholly typical member of the 

 Sphaeriaceae" (Ann. Myc. 16:35, 199 1918). 



The final blow to the Pseudosphaeriaceae was delivered by Petrak five 

 years later. "The comparative study of a large number of forms, regarded 

 either by Hoehnel or Theissen or by both as Pseudosphaeriaceae, has shown 

 that, while these are actually of the greatest importance for the taxonomy 



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