New York AGRICULTURAL EXPERIMENT STATION. 69 
seed are equally affected. It lies rather, as will be later shown 
(page 76), within the control of the individual purchaser. 
VITALITY OF GERMS ON SEED. 
Even though large numbers of P. campestris are attached to 
the seed at the time of harvest it does not necessarily follow 
that they will survive long enough to affect the succeeding crop. 
P. campestris does not form spores and consequently is not well 
fitted to withstand adverse conditions for a long period. Upon 
the surface of the smooth, hard, cabbage seed, food is scarce; 
and moisture, which is so necessary to the life of the germs, is 
reduced to a minimum. The close dependence of P. campestris 
upon moisture is shown by its rapid destruction when exposed 
to dessication. 
EFFECT OF DESSICATION oF P. campestris. 
This point was previously tested by one of us (H) at the Wis- 
consin Station’? by allowing a small drop of fresh bouillon cul- 
ture of the organism to dry upon sterile cover slips, which were 
kept in darkness at room temperature. 
In the limited number of tests which were made at that time 
the germs all died within 45 hours. 
After the somewhat surprising results from our tests of the 
vitality of P. campestris upon cabbage seed, the tests upon cover 
glasses were repeated using the same organism which had _ been 
used to infect the seeds and carrying on the test under conditions 
which would be closely comparable to those to which the seeds 
were exposed. 
The cultures used at Wisconsin had been grown in the labora- 
tory about a year at the time of the test and the results may be 
open to some objections on that score. In order to be sure in 
the present instance that the culture was as nearly as possible in 
its natural condition it was first inoculated into a cabbage plant. 
There it produced the characteristic lesions of black rot. From 
these plants the culture was isolated and its purity determined. 
The growth upon agar slope, two to three days old, was then 
rubbed up in sterile water as thoroughly as possible and the 
emulsion filtered through paper. This gave a faintly milky solu- 
tion containing a very great number of individuals but free from 
lumps and large masses of germs. 
"Wis. Agr. Exp. Sta. Bull. 65:19, 1898. 
