12 BULLETIN 1029, U. S. DEPARTMENT OF AGRICULTURE. 
A limiting factor in the use of mercuric-chlorid solution is the fact 
that complete contact with the seed coats is usually prevented by the 
presence of small air bubbles. To overcome this difficulty Hutchinson 
and Miller (4) conducted their seed treatments in partial vacuum, 
but with only limited success. Since two trials with infected seed by 
this treatment in 1 : 500 mercuric chlorid gave no better results than 
parallel experiments at atmospheric pressure, the method was aban- 
doned (see Table IV). 
In order to overcome this difficulty in another way the seed was 
soaked in water previous to treatment (method 3). The action of 
the fungicide on the seeds was more rapid than with the unsoaked 
seed, marked injury resulting from treatments of more than 30 min- 
utes' duration. At this point, however, the disinfection of diseased 
seed was no more complete than with similar exposures of unsoaked 
seed. 
In the fourth method of treatment, where seeds were rinsed in 
alcohol before exposure to the mercuric-chlorid solution, the action of 
the disinfectant was hastened somewhat, injury to the seed being 
pronounced after a treatment of one hour (see lot No. 4-19, Table 
IV). The method appears to be no more effective than the first, how- 
ever, in eradicating the fungus from infected seeds. 
The results with mercuric chlorid may be summarized as follows : 
With most lots of seed used a soaking of one hour in a 1 : 500 solution 
followed by rinsing in water caused very slight seed injur} 7 . One 
lot, however, was injured considerably by this treatment. Treatment 
was necessary for two hours for complete eradication of the fungus 
in the case of one lot of infected seed, and in another lot treatment 
for three hours was insufficient to attain this result. Other methods 
used with mercuric-chlorid solution — (1) soaking in the disinfectant 
without rinsing after treatment, (2) presoaking in water before treat- 
ment, (3) dipping in alcohol before treatment, and (4) treatment in 
partial vacuum — did not appear to be superior to the first. For 
general use soaking for 30 minutes in a 1 : 1,000 solution, followed by 
rinsing in water, is advisable. Most lots of seed will stand a 1 : 500 
solution for a somewhat longer time, but preliminary trials should 
be made before this stronger treatment is applied. 
SUMMARY OF LABORATORY SEED-TREATMENT EXPERIMENTS. 
The data presented justify the conclusion that no known method 
of cabbage-seed disinfection can be relied upon for the complete 
eradication of the black-leg fungus, Plwma ling am, without severe 
injury to the seed. It is also evident that different lots of seed vary 
widely in their relative susceptibility to injury from seed treatment. 
This forces one to be the more conservative in recommendations for 
general practice. The results of experiments lead the writer to 
