196 BACTERIA IN RELATION TO PLANT DISEASES. 
that we want to increase the efficiency of the test, if we can, by the addition of some form of organic 
matter, which will aid us in determining the real efficiency of disinfectants in the presence of organic 
matter. This point is especially important in connection with disinfectants which act by oxidation. 
If you try permanganate of potash on naked organisms you will find that it is very efficient, but if 
you mix with it a little dust you will find that its power has largely gone down.” 
Dr. Schryver in the discussion also cited the physical action of organic matter held in suspen- 
sion as well as in solution and considered this to be important. 
GERMICIDAL TREATMENT OF SEEDS. 
Seeds with a thick impenetrable seed-coat offer no special obstacles to thorough dis- 
infection. All that is necessary is actually to wet every part with a strong germicide for a 
sufficient length of time. To insure this wetting there should be a brief preliminary wetting 
in alcohol that air may be driven out of all the minute crevices where otherwise the germi- 
cide would not penetrate. 
The case is quite different, however, with seeds having delicate and easily permeable 
seed-coats. These have to be treated with great care, and often it is not possible to dis- 
infect their surface thoroughly without at the same time destroying the embryo, at least 
in a large proportion of the seeds. Sometimes in such cases we may reach the end desired 
indirectly, z.e., by not allowing the seeds to become infected, since they are always originally 
sterile inside the unopened pods. To obtain sterile seeds it is suggested that the unopened 
seed-pods be collected with great care and their surface treated with germicides or fire, or 
both, after which the pods must be carefully opened (in still air), and the seeds removed by 
means of sterile forceps (see fig. 2, and p. 135). 
The writer found that 15 minutes’ exposure of hard dry kernels of sweet corn to 1:1000 
mercuric chloride did not entirely sterilize the surface, although from the results obtained 
it must have come very near to doing it, so far as regards the death of the organism in 
question, 7. e., Bacterium stewart. 
Experiments made by the writer in the summer of 1909 with hybrid dent corns and 
sweet corns having a high germinating capacity showed that the dry kernels would stand 
exposure to 1:1000 mercuric chloride water for 20, 30, 40, and 50 minutes with little injury, 
the kernels being placed at once in damp sand after preliminary rinsing in hydrant water 
or without rinsing. Nearly all germinated promptly and the seedlings looked as well as 
those from the untreated seeds. 
In the first series twenty seeds were planted in each pot and the following are the 
number of germinations per pot, the count being made on the sixth day: 
(1) U.S. P. B. No. 100 (field-corn) : 
Checks, 20, 20, 20, 19, 19; Checks, — none. 
Mercuric chloride (20 minutes), 18, 20, 17, 19, 19; Mercuric chloride (30 minutes), 18, 19, 18, 19, 20. 
In a second series of tests, using 20 seeds and counting on the fifth day, the follow- 
ing results were obtained: 
(2) U.S. P. B. No. 120 (field-corn) : 
Checks, 14, 18, 14, 17, 16; Checks, 16, 15, 17, 16, 18; 
Mercuric chloride (40 minutes), 18, 19, 15, 19, 12; Mercuric chloride (50 minutes), 18, 17, 16, 18, 20. 
There was no marked difference in the appearance of the seedlings. 
The experiments were repeated a few days later with this difference only, that the 
seeds were not rinsed, but dried promptly and planted at once with the mercuric chloride 
adhering to them. The results on the sixth day were as follows: 
(1) U.S. P. B. No. 100 (field-corn): 
Checks, 18, 20, 20, 19, 20; Checks, 18, 19, 20, 19, 20; 
Mercuric chloride (20 mintites), 19, 18, 16. 19, 17; Mercuric chloride (30 minutes) 18, 20, 19, 20, 19. 
The treated seeds showed a slight retardation in germination. Checks 2 to 3 inches 
high; treated 1.5 to 2 inches high. 
