. Carnegie Institution of Washington publication. 304 BACTERIA IN RELATION TO PLANT DISEASES. one to discriminate. The lapse of a little time between inspections will also help one to judge, since in its further progress the black rot is quite different from the other foliar diseases. In this connection see plate 18. ETIOLOGY. The cause of this disease is a yellow one-flagellate micro-organism, Bacterium campestre (Pammel) EFS. Conclusive proof of the infectious nature of this organism was obtained on turnips by Pammel in 1893 and pub- lished in 1895. He performed 20 direct inoculations succes
. Carnegie Institution of Washington publication. 304 BACTERIA IN RELATION TO PLANT DISEASES. one to discriminate. The lapse of a little time between inspections will also help one to judge, since in its further progress the black rot is quite different from the other foliar diseases. In this connection see plate 18. ETIOLOGY. The cause of this disease is a yellow one-flagellate micro-organism, Bacterium campestre (Pammel) EFS. Conclusive proof of the infectious nature of this organism was obtained on turnips by Pammel in 1893 and pub- lished in 1895. He performed 20 direct inoculations successfully. Subsequently he isolated the organism. His pure cultures were derived from turnips and rutabagas, and 8 successful inoculations were made into rutabagas, as many plants being held for control. The signs of the disease ap- peared in the course of a few days, finally involving the whole plant; this same or- ganism was subsequently isolated from the diseased tissues, i. c, from the blackened bundles and advancing margin of the rot. In 1896-97 the writer repeated and con- firmed Pammel's experiments on turnips and rutabagas and extended the inocula- tions to cabbages, cauliflower, kale, rape, radish, and black mustard. Two strains of the organism were used for most of these infections, viz., pure culture isolations from diseased turnips obtained in Maryland and similar cultures from diseased cabbages from Wisconsin, but some cross-infections were also made with the organism obtained from charlock in Wisconsin. Microscopic examinations, bacteriological cultures and cross-inoculations showed the disease to be identical in all of these plants.* He also confirmed and considerably extended Pam- mel's description of the organism. The writer at this time had obtained altogether more than 60 successful infections resulting in typical cases of the disease. From dis- eased plants at long distances from the point of inoculation he several times re- isolated the organism and obtained a
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