Fungous Flora of the Soil 501 



Failure of the writer to isolate Rhizoctonia from Long Island soil that 

 was growing a crop of diseased potatoes may be explained on either of 

 the two following grounds : the fungus does not live as a saprophyte in the 

 soil, but is carried over winter on the seed; or the fungus may have been 

 overgrown in the plates by more rapidly growing species, such as some of 

 the species of Mucor or Fusarium. Species of both genera were present 

 in the plates. 



Soil three months after application of sulfur yielded the same species 

 of fungi as did the soil that had had no such application. 



The taxonomic considerations include the presumable facultative para- 

 sites of the soil, with references to literature but no descriptions; and the 

 obligate saprophytes that have been isolated from the soil thus far, 

 together with standard descriptions. The whole includes some one 

 hundred and thirty-two species and varieties. 



CONCLUSION 



The need is urgent for a study of the fungi in soils generally recognized 

 as sick to some particular crop, as well as of the relation of these fungi to 

 crop rotations, fertilizers, and fungicides. Do not the debris of the crops 

 in the rotation serve as excellent pabula for the fungi that produce the 

 disease in question? Which crops are of this nature? What effect on 

 the soil fungi results from the addition of various kinds of fertilizers? 

 Is the application of fungicides such as sulfur effective in changing the 

 fungous flora? If so, in what way? These are but a few of the questions 

 that need elucidation. 



More should be known of those fungi generally recognized as facultative 

 parasites. Are not some of the species carried over from year to year on 

 or in the seed, or do they live as saprophytes in the soil during the winter? 

 Too often it is said without the proper evidence, that a fungus is a soil 

 organism. The ease with which error can be made is shown by the fact 

 that, with the exception of the past two or three years, since 1895 Phoma 

 Betae Fr. has been considered as living in the soil in sugar beet sections. 

 It is now quite conclusively demonstrated to be carried over on the seed 

 balls and not in the soil. It seems to the writer thai if a more detailed 

 and far-reaching study were made of this phase of the question, it would 

 be far more remunerative in many instances than a study of the control 

 alone, after fungi have made a sick soil. 



