THE CONTROL OF CABBAGE BLACK-LEG, 5 



by seed-bed trials on silt-loam garden soil at Madison and on sandy 

 soil at Racine, Wis. 



In rinsing seed after treatment with mercuric-chlorid or formalde- 

 hyde solution one thorough washing in clean tap water was made. 

 As pointed out by Robinson {9), who showed that a slight amount 

 of the former fungicide was present in the fourth wash water after 

 treatment of pea, bean, vetch, and barley seeds, it is probable that 

 this one rinsing was insufficient completely to remove the fungicides. 



HEAT AND DESICCATION. 



Atanasoff and Johnson (1) have given a summary of previous 

 work on the relation of high temperatures to the viability of various 

 seeds. They studied further the effect of dry heat upon barley, 

 wheat, rye, and oat seeds and upon a number of seed-borne organ- 

 isms. It was concluded that the bacteria causing blights of barley 

 {Bacterium translucens) and of oats {Pseudomonas avenae) could 

 be successfully eradicated from infected seeds by dry heat, while 

 several fungous parasites of cereals were either eliminated or 

 markedly reduced by the same treatment. Harrington and Crocker 

 {£) found that the percentage of germination of wheat, barley, 

 Sudan grass, Kentucky bluegrass, and Johnson grass was not mate- 

 rially changed when the moisture content was reduced to less than 

 1 per cent by drying over calcium oxid or sulphuric acid at room 

 temperature. Waggoner (10), by drying radish seeds first at 60° C. 

 and then at 100° C, reduced the moisture content from 4 per cent at 

 normal air-dry condition to 0.4 per cent without reduction of germi- 

 nation. 



In the experiments reported here several lots of cabbage seed, 

 varying in age from a few months to 7 years, were reduced to con- 

 stant weight at 100° C. In these lots the moisture content of the 

 air-dry seeds, untreated, remained around 6 or Y per cent of the 

 dry weight. The results given in Table I show that at 85° C. the 

 moisture content dropped rapidly during the first 6 hours and 

 then became nearly constant after 48 hours. Seed treated with mer- 

 curic-chlorid solution became adjusted to its original air-dry mois- 

 ture content within a few weeks. 



All of the drying experiments reported were carried out in a Freas 

 constant-temperature electric oven. Seeds were placed for this pur- 

 pose in thin layers in small paper containers, so as to avoid direct 

 contact with substances of high specific heat. 



Desiccation at high temperatures (85° to 95° C.) caused a gradual 

 reduction in viability, which was accompanied by retardation in 

 germination and growth. The plants might outgrow the effects of 

 mild treatments, but severe injury was usually permanent. In the 

 early experiments, in which No. 3-18 seed was used, only slight in- 



