16 



Levi Otto Gratz 



Inoculation experiments 

 Susceptibility of different varieties of Brassica oleracea L. 



"All Seasons " was the variety of cabbage used in all of the preceding 

 as well as the following experiments. Six early, nine late, four red, and 

 three savoy varieties also were tested, and in addition five varieties of kale, 

 four varieties of cauliflower, and one of brussels sprouts. None showed 

 any degree of resistance. When the few plants that did not exhibit wire 

 stem at the first count were reinoculated by placing some infected soil 

 directly about the stems, damping-off occurred in every instance within 

 twenty-four to forty-eight hours. After the observations were made, 

 the checks were likewise inoculated, with similar results. Thus a total of 

 about 250 seedlings of each variety were tested. 



Susceptibility of other species of plants 



The strain from cabbage was found to be pathogenic on eleven of the 

 thirteen hosts inoculated (table 6). These hosts represent eleven species, 



TABLE 6. 



Results of Inoculation of Different Hosts with the Strain of 

 corticium vagum from cabbage 



* d, damping-off; 1, stem lesions; +, very slight; + +, definite. 



eleven genera, and six families. No infection resulted when onion seedlings 

 or potato stems were inoculated. 



Susceptibility of plants of different ages 



It is generally held that tender, succulent seedlings are very susceptible 

 to damping-off, and that as the plants grow older this susceptibility 

 gradually decreases. It is supposed that as the tissues become harder 

 and older there is reached a stage of maturity after which the stems are 

 practically immune. In order to obtain information on this point, seed 

 was sown in sterilized soil at intervals of two weeks, and the plants were 



