426 Bulletin 315 



of the nature produced by Pythium de Baryanum Hesse and Aphanomyces 

 laevis de Bary occurred in soil that contained these organisms. (These 

 organisms are not in all soils, which is to be expected ; still they are quite 

 generally distributed in Germany.) With the use of completely sterilized 

 soil and unsterilized seed-balls, " Wurzelbrand " produced by Phoma 

 Betae Fr. occurred. The authors conclude that Phoma Betae Fr. does not 

 live from season to season in the soil, but that it is carried over on the 

 seed-balls; on the other hand, Pythium de Baryanum Hesse and Aphano- 

 myces laevis de Bary live as saprophytes in the soil, and under suitable 

 conditions they can attack the beet. In passing it should be stated that 

 the mmiber of soils tested was more than sufhcient to warrant the con- 

 clusions. Some of the soils had not been in beets since 1899; some since 

 1902, 1903, and 1904; others had been in beets in 1908, when this work 

 was completed. 



That Phoma Betae Fr. can be carried over winter in the soil is supported 

 by Frank ('95). From the nature of his investigations and the evidence 

 against his view, we may conclude that his point is not well taken. 



From the above data, it must be accepted that Pythium de Baryanum 

 Hesse and A^phanoniyces laevis de Bary constitute a part of the soil flora; 

 and that Phoma Betae Fr. has not as yet been proved to live in the soil. 



Manns ('11) has worked with Fusarium oxysporum Schlecht. (Fusarium 

 orthoceras Appel), causing the dry rot of potatoes. The evidence to the 

 effect that this fungus may live in the soil is similar to that just given with 

 respect to Pythium de Baryanum Hesse and Aphanomyces laevis de Bary. 



Finally, it should be stated that there are many plant pathologists who 

 have given rather convincing circumstantial evidence to allow the accept- 

 ance that certain facultative parasites, as Fusarium, vasinfectum. Atk., 

 Pythiacystis citrophthora R. E. & E. Smith, Oospora scabies Thaxter, 

 Thielavia basicola (B. & Br.) Zopf, and others, can live as pure saprophytes 

 in the soil for a period of several years. However, space will not allow of 

 a presentation of this evidence. 



PRESENT INVESTIGATIONS 



Soils examined 



The writer's investigations were restricted to a study of the fungi in 

 arable soil. The original plan was to take a soil sample every month of 

 the year from the same field. This plan was later partially abandoned. 



('95) Frank, A. B. Neue Untersuchungen iiber Phoma Betae. Zeitsch. Ver. 

 Rubenzuckerind. D. R. 45: 180 and 272. 1895. 



('11) Manns, T. F. The Fusarium Blight and Dry Rot of the Potato. Ohio Agr. 

 Expt. Sta. Bui. 229: 316-317. 191 1. 



