l8o BACTERIA IN RELATION TO PLANT DISEASES. 



plants which yielded no bacteria at this level were now cut off just above the roots and a third set of 

 tubes inoculated from the inner tissues, all of which now yielded this organism. As this positive 

 result was not in accord with the previous experiments and might perhaps be attributed to injury 

 of the roots during removal from the pots, the following experiment was undertaken. 



Beans were planted in a nutrient fluid consisting of: water looo: potassium nitrate 0.5, potas- 

 sium phosphate 0.2, magnesium sulphate 0.2, ferrum sulphate o.i. They grew well in this fluid and 

 when about 20 cm. high a culture of Bact. pyocyaneum was added. The roots of some of the plants 

 were purposely injured, while the others remained sound. After some days cultures were made from 

 the interior of the plants. These showed the presence of Bact. pyocyaneum in all the injured plants, 

 and in none of the uninjured ones. 



Bllrodt's conclusion, therefore, is that bacteria can not penetrate sound roots, but may 

 enter through broken ones, and that since root-injuries are common occurrences in soil, 

 it is not yet certain that pathogenic bacteria can not enter the plant from infected soils. 



Clauditz criticises Elb-odt for not telling in what tissues the bacteria occiurred. Fur- 

 thermore, inasmuch as he does not state that he washed or otherwise removed the bacteria 

 from the surface of the plants, he may really have got his results from surface organisms, 

 which were dragged into the tissues. Certainly, the surface of his plants, particularly the 

 parts near the roots and consequently near the bacterial fluid, should have been flamed or 

 otherwise disinfected. In the last mentioned experiment, however, he probably did not 

 get his results from surface organisms because his checks were sterile. 



Clauditz (1904) made a series of experiments with the typhoid bacillus to learn whether 

 infection through plants is possible and especially whether this organism can penetrate 

 into the interior of plants. In certain respects his statements also are vague. 



Clauditz used the plants which are commonly eaten raw, viz., radish, cress, and lettuce. The 

 soil was taken from the yard of the Hyg. Institixte of the Royal University of Berlin. To imitate 

 as nearly as possible the conditions of the soil in the sewage fields several glass tubes were thrust into 

 the earth a depth of 8 cm., and 24-hour old bouillon cultures of the typhoid organism were poured 

 into these tubes every other day. After 8 days, repeated attempts were made to recover the organism 

 from the soil, but these failed in spite of renewed infections with a fresher isolation. These cultures 

 were made both from the surface and from 4 to 6 cm. down. 



He states that it is difficult to isolate the typhoid organism from the earth because in most 

 cases this organism quickly perishes when brought into competition with the bacteria of the soil. 

 Following RuUmann's advice he mixed the infected soil with double its quantity of sterile bouillon 

 and incubated at 37°, but always the soil organisms got the advantage and the typhoid bacillus was 

 not to be recovered in this way. He then tried to accustom the typhoid organism to the soil bacteria 

 in bouillon cultures by adding to sterile bouillon a loop of a 24-hour bouillon culture of B. typhosus 

 and 2 loops of soil and exposing for 24 hours at 37° C. From this tube 3 loops were then transferred 

 to a second tube which was incubated for the same time and at same temperature, and so on for 10 

 tubes. After 5 days the typhoid organism was not demonstrable in the first tube, and not after 24 

 hours in the second, while in all the others the results were negative. 



The strain isolated from the second tube was designated "Typhus Erde I." With this a second 

 series of 10 tubes was inoculated in the same way as before. The results from this set of tubes were 

 all positive, and even after a half year the typhoid organism was easily demonstrated in tube 10. 

 Along with it were present a variety of other bacteria. Bacillus subtilis, Bact. fluorescens liquefaciens, 

 cocci, etc. 



A second set of soil inoculations was undertaken with this strain, "Typhus Erde II," the 

 bouillon cultures being now poured into the soil after dilution with sterile distilled water. It was 

 now easy to demonstrate the bacillus in the soil and a strain so isolated was called " Typhus Erde III." 

 The latter was now used for all the subsequent experiments. 



After the organism had been isolated from the soil and when the plants were 5 to 8 cm. high, 

 they were cut off close to the earth with a sterile knife, washed one-half hour in sterile water, bruised 

 in a sterile mortar with sterile bouillon and then incubated for 24 hours at 37° C. Streaks were then 

 made on Drigalski-medium, one out of four being positive. The experiment was repeated with the 

 precaution first to put the plants in a i :ioo solution of mercuric chloride (time not stated) and then 

 wash them thoroughly in sterile water. All the tests were now negative. To avoid the objection 

 that the mercuric chloride may have penetrated the plants and killed the bacteria, the experiment 

 was repeated, the surface of the plants being sterilized this time (so far as regarded B. typhosus) by 



