BLACK ROT OF CRUCIFEROUS PLANTS. 305 
In Wisconsin, Russell & Harding repeated the experiments of Pammel, and of Smith, and 
confirmed their conclusions respecting the bacterial nature of the disease. Harding also 
studied the morphology and physiology of the organism quite carefully. The number of 
their successful infection experiments amounted to several hundred. In New York and in 
Europe, Harding subsequently continued his studies. On his return from Europe he 
obtained numerous successful infections on cabbage and cauliflower with a culture which 
he isolated from a diseased cabbage-plant found by him in Switzerland. Comparative 
tests were also instituted and neither in its cultural characters nor in its infectious proper- 
ties was any difference detected between the Swiss organism and the one from New York 
or Wisconsin. 
Hecke subsequently discovered the disease in kohlrabi in Austria and published two 
instructive papers on it, the number of his 
infection-experiments exceeding 100, Rus- 
sell, however, was the first to obtain the 
disease in kohlrabi by inoculations (Bull. 
65, p. 22). Van Hall then studied it in 
cabbages in Holland. More recently 
Brenner in Basel, under direction of Dr. 
Alfred Fischer, investigated the etiology 
of this disease, and after experimenting 
for two seasons states that he can only 
confirm Smith’s conclusions respecting the 
cause of this disease. 
The writer has himself isolated this or- 
ganism from diseased plants obtained 
from Illinois, Wisconsin, Michigan, Ohio, 
Pennsylvania, Western New York, Long 
Island, Maryland, Alabama, Florida and 
Texas, and has studied the disease in the 
field in half a dozen different States. He 
has also produced the disease in cabbage 
by inoculating with a pure culture of the 
organism received from Hecke, who iso- 
lated it from kohlrabi grown in Southern 
Austria and himself proved its infectious 
nature on a variety of crucifers. In most 
of the above mentioned isolations by 
means of poured plates, Bacterium cam- 
pestre was found in the vessels of the Fig. 103.* 
plants in pure culture. Only occasionally 
were mixtures obtained and even then the yellow organism was the preponderant form. 
Plants are attacked by this disease in all stages of growth from seedlings in the seed- 
bed to plants ready for the market. In all this class of plants most of the infections, perhaps 
all of them in plants beyond the seedling-stage, are through the parts above ground and 
generally by way of the leaves. The writer, who has spent many weeks in cabbage-fields, 
has never seen anything in midsummer or later suggestive of infection through the root- 
system, 7. ¢., roots diseased and parts above ground not diseased, and Hecke’s experiments 
of growing plants in soil mixed with tissues swarming with the organism, yielded only nega- 
tive results. So did my own. Brenner also made similar experiments with similar results: 
*Fic. 103.—Longitudinal section and cross-sections of stems of cauliflower diseased by Bacterium campestre, 
showing stain and cavities in the stems. Miami, Fla., March, 1904. 
