THE CONTROL OF CABBAGE BLACK-LEG. 7 



It will not be necessary to consider in detail the data obtained when 

 the seeds were exposed at 90° and 95° C, as listed in Table I. Lot 

 No. 3-18 again proved to be the most resistant, while the remaining 

 lots, as a rule, received marked injury at these temperatures. Parallel 

 treatments of highly infected seeds showed that the fungus had been 

 killed within 18 hours at 95° C. and within 96 hours at 85° C. Both 

 of these treatments might, therefore, be of practical use with lot No. 

 3-18, but would be very injurious to the other lots. 



A quantity of No. 3-18 seed was dried first at 87° to 50° C. for five 

 days, then at 73° C. for three days, by which means the moisture con- 

 tent was reduced to 1.31 per cent. The seed was then placed in an 

 incubator running at 100° C. The results (Table I) showed that in 

 spite of the reduced water content the ability to resist this high tem- 

 perature was not increased. Agar-plate tests with badly infected 

 seed similarly treated were not made. However, a sample dried at 

 40° to 50° C. for 19 days and then at 85° C. for one day, the moisture 

 content being reduced to 1.44 per cent of the dry weight, yielded 

 almost as much disease as untreated seed in seed-bed trials. This fact 

 indicates that prolonged drying at moderate temperatures does not 

 materially affect the fungus. 



It is evident from the foregoing data that cabbage seed is not uni- 

 formly resistant to desiccation at high temperatures. Moreover, the 

 fungus within or beneath the testa is so resistant to this treatment 

 that complete eradication of it from infected seed by baking is im- 

 possible without considerable injury to the seed. These facts, to- 

 gether with the difficulty of applying this treatment on a large scale, 

 give doubtful value to this method for commercial use with cabbage 

 seed. 



FORMALDEHYDE SOLUTION. 



In the trials with formaldehyde solution use was made of formalde- 

 hyde, standard strength of approximately 40 per cent, diluted with 

 distilled water. Aside from one treatment with a 1 : 256 solution for 

 37 minutes, which was approximately the same as the formula used on 

 a commercial scale in 1918, the stronger concentration (1:128) was 

 used throughout the experiments with formaldehyde. Unless other- 

 wise noted the solutions were used at room temperature, approxi- 

 mately 20° C. Certain of the lots were rinsed in clean water ; others 

 were not rinsed. All were spread out in thin layers after treatment 

 and allowed to dry under laboratory conditions. As will be seen from 

 the results given in Table II, the latter treatment always produced 

 greater injury than resulted in the case of corresponding rinsed lots. 



The deleterious effect of formaldehyde upon cabbage seed becomes 

 evident both as reduction in percentage of seed germination and as 

 injury to the seedlings. The data in Table II show a progressive 

 decline in the percentage of germination of commercial seeds with the 



