144 



Journal of Agricultural Research 



Vol. IV, No. 3 



pot and to examine daily for damping-off. Whenever disease occurred, 

 the plants affected were removed and a record made of their number. 

 The period of greatest susceptibility seemed to be passed by the time 

 the third set of leaves appeared. After a sufficient period the remaining 

 plants were harvested and examined for signs of infection on the roots. 

 The following record (Table IV) of a typical series illustrates the 

 method and gives a good idea of the average results. 



Table 1Y .—Results of inoculation experiment with Phoma betas 



The plants described as diseased were typical root-sick beets. There 

 was nothing about their appearance aboveground in the pots to indicate 

 the presence of the fungus, but in the field such seedlings may often be 

 detected from the fact that they appear to be suffering from lack of 

 moisture. This type of disease is almost universal under field conditions 

 and is far more common than damping-off. Histological studies upon 

 such material, to be published in a subsequent paper, revealed the sig- 

 nificant fact that it often carries the pycnidia and sometimes the vege- 

 tative mycelium of the fungus. 



The number of seedlings developing in control pots was, as a rule, 

 larger than the total number developing in inoculated ones. This is to 

 be explained by the fact that some of the seedlings were attacked before 

 they broke the ground and in consequence were unable to push through 

 the soil. A careful examination of the surface soil in inoculated pots 

 now and then revealed such seedlings in a state of more or less complete 

 decay. 



PHOMA FIEI.D-ROT AND STORAGE-ROT FOLLOWING SEEDLING INFECTION 



When diseased plants were allowed to remain in the pots and were 

 held under as favorable conditions as possible, a large proportion of 

 them eventually survived and sent out new roots. This condition is 



