So es eS —— ~ le Mn ie Oe a, ae " i naa) 
186 BACTERIA IN RELATION TO PLANT DISEASES. 
Il y aen effet du danger a faire ces expériences portant sur des microbes pathogénes en pleine 
terre. 
: To obtain conditions more nearly approximating those found in the fields they experimented 
with Bacterium violaceum and the red Kiel bacillus. 
Seeds of radish were sowed in the open field, were covered with about 2 cm. of earth and were 
watered with a culture of Bact. violaceum suspended in sterilized water. It was at this time very warm 
and dry. The radishes were watered very abundantly by showering with ordinary water. Fifteen 
days after.the sowing the plants were lifted and a search made for the bacillus, but it could not be 
found either on the surface of the plants or in the earth where it had been put. 
The same experiment was repeated using the Kiel bacillus, but dividing the field into two parts, 
one of which was shaded, and the other exposed to the sun. The weather continued very hot and the 
artificial waterings were abundant. The Kiel bacillus was recovered on plate cultures from the sur- 
face of the plants grown in the shade, but not from those exposed to the sun, so that we must assume 
either that the sun destroyed the bacteria, or did away with their pigment production. In the above 
experiments [probably those with the pigment-forming bacteria] the plants were exposed to the infec- 
tious water after they had begun to develop. : 
To test the ability of the plant to bring up bacteria out of the depths of the soil they made the 
following experiments. 
Potato tubers were wet on the upper surface with a virulent, sporulating bouillon culture of the 
anthrax organism (about one culture for each three potatoes). They were then placed in boxes of 
earth and covered with from 5 to 10 cm. of vegetable earth. From March 21 to July 1 these potatoes 
were watered with large quantities of water, as well before as after the development of the shoots. 
During growth the plants were watered several times a week. In May and June the plants were 
exposed to sunshine from morning until 3 p. m. 
Fragments of the leaves and stems were taken with sterile instruments and washed in bouillon 
which was then heated for 5 minutes at 80° C. This bouillon was then used for gelatin plates, 10 drops 
being put into each plate. In this way the anthrax organism was recovered 41, 93, and 101 days 
after the sowing, and at heights of from 4 to 30 cm. above the earth. The anthrax organism was 
constantly present, but usually only a few colonies developed, on an average 1 or 2 per plate. At 
the end of 3 months these anthrax spores had lost half their virulence. 
To reassure themselves of this and to do away with the effect of other soil organisms (Vibrio 
septique, tetanus, etc.) this experiment was repeated in sterile soil. Anthrax colonies taken from the 
tops of the stems of potatoes grown in this soil had lost their virulence. 
In spite of the action of light and of rainfall, there is, therefore, according to Wurtz and Bourges 
some reason for suspecting vegetables grown on lands devoted to the purification of sewage, even 
though theoretically the sewage be not deposited in a sheet on the surface of the soil, since plants, as 
well as animals, may serve to bring pathogenic bacteria to the surface of the earth. 
