170 BACTERIA IN RELATION TO PLANT DISEASES. 



not make use of the by-products of these bacteria, but nourishes itself at the expense of 

 the bacteria themselves. 



"Die enorme Zahl von Bacterien, die Dictyostelium mucoroides verdaute, und seine geringen Anforderungen an 

 die Ernahrung erklaren es, dass Bacterien den Hauptbestandtheil seiner Nahrung bilden und fur ein massiges, wenn 

 nicht reiehliehes Wachstum geniigen." 



In a second paper Pinoy states that he freed spores of Dictyostelium mucoroides from 

 the presence of Bacillus fluorescens liquefaciens by exposing them to a temperature of 50 

 for one hour. Under these conditions the bacteria were killed but the spores of the myxo- 

 mycetes were not killed. Such spores germinated readily in the presence of various bacteria 

 e. g., Bacillus fluorescens liquefaciens, Microbacillus prodigiosus, Bacillus coli, etc. They 

 did not germinate when sown by themselves. The development of the myxomycetes was 

 more or less abundant according to the bacterial species used in connection with it. When 

 fluorescent bacteria were used the Dictyostelium became a yellowish color. On the contrary 

 when the Bacillus prodigiosus was used the spore-heads were white with a very slight 

 tint of rose color. 



Vuillemin has also published a note on this subject. He states that he cultivated 

 Dictyostelium mucoroides in test-tubes, cotton plugged, on agar containing 0.5 per cent 

 peptone and 0.2 per cent maltose, at laboratory temperature, protected from the light. 

 The sowings were made from white spore heads and these often contained bacteria which 

 he states to have been a fetid fluorescent species. All the tubes which showed any growth 

 of Dictyostelium also contained the bacteria. The fruiting pedicles appeared the third day. 

 If the sowings had not developed any bacteria there was no visible growth of the myxo- 

 mycetes, although the microscope showed amoeba-formed bodies to have issued from the 

 spores. To obtain growths of the myxomycetes from these apparently sterile tubes it was 

 only necessary to introduce a culture of the bacillus. When pyocyanic bacteria were 

 substituted the results were negative. 



Nadson believed that the bacteria rendered service by producing an alkaline substratum. 

 Vuillemin states that the bacteria do not act indirectly, by modifying the substratum, but 

 that they serve directly as food for the amoeboid bodies of the myxomycetes. 



Nadson, whose paper is earlier than any of those already referred to (1899), states 

 that he obtained absolutely pure cultures of Dictyostelium mucoroides, but that these were 

 weak dwarfed forms, giving generally no proper conception of the species. He also speaks 

 of a symbiosis and says that the ordinary companion of this myxomycete is Bacillus fluo- 

 rescens liquefaciens Flugge. 



In 1905 Pinoy published a paper on the role of bacteria in the devolpment of Plasmo- 

 diophora brassicae, the myxomycete occurring in hernia of the cabbage. 



He found in pieces of young tumors of cabbage obtained by experimental infection, 

 that some cells invaded by the parasite contained also masses of bacteria (forms of cocco- 

 bacillus occurring either singly or in pairs). 



He followed this microscopic work by cultures as follows : 



The surface of large tumors, showing no trace of decay was burned deeply with a hot iron, and 

 portions removed by means of flamed pipettes. The spores of the parasite contained in great num- 

 bers in this material were sowed on the ordinary media and produced numerous colonies of bacteria. 

 He thinks, therefore, that the bacteria were introduced into the root of the cabbage by the parasite. 

 What role do they play? 



Pieces of healthy young turnip were removed aseptically by means of a sterile punch (Borrel's), 

 placed in flamed tubes and sowed with the spores of the fungus. The tubes were then sealed in the 

 flame and placed in the thermostat at 22 C. During the first days scattered colonies of aerobic 

 bacteria arose, which, however, ceased to grow when the oxygen was exhausted. Five days after 

 sowing, the cells of the turnip contained Plasmodiophora in various stages. Many cells were filled 

 with spores. When the same experiment was carried on in tubes plugged with cotton, i.e., exposed 

 to the air, the aerobic bacteria which accompanied the spores developed more abundantly and 

 brought about the decay of the turnip. When anaerobic bacteria were accidentally introduced the 

 growth of the myxomycete was stopped. 



