246 BACTERIA IN RELATION TO PLANT DISEASES. 



observed between slight marginal injury and penetration of the bacteria through the side veins, into 

 the midrib, and even into the vessels of the stem. The general conclusion from this examination 

 may be stated as follows: "So long as the seedlings stand in the row they are more likely to be infected 

 in the leaf than in the root. " Whether the attacked seedling is planted out depends a great deal on 

 the age of infection. If it is somewhat advanced an intelligent coolie would reject it. On some 

 plantations the rule is: " No seedlings shall be planted except those on which the lowermost leaves are 

 still good. " But this rule involves the destruction of many good seedlings. Also, it is not always 

 the lowermost leaves that are first infected. The best proof that such leaf-infected seedlings can 

 yield infected plants is the finding of plants in the field with diseased stems and sound roots. Such 

 plants have been seen as early as a month after planting. 



Diseased seedlings, however, are not the only cause of diseased tobacco in the fields. This was 

 well shown in a field where a great many of the plants died. This field was planted in part, it is true, 

 from an infected seed-bed, but also in part from a sound bed, which on higher land yielded sound 

 plants. Here the soil of the field, which had stood under water, was infected. A similar case was 

 observed on another plantation. 



The water used for irrigation may be also a source of infection. Up to this time the water of 7 

 wells used for this purpose has been examined and the slime-bacteria found to a certainty in 4 of them 

 on 3 different plantations. Because of the organism's need of free oxygen these wells are believed to 

 have become superficially infected by the falling into them of infected earth rather than from the 

 ground-water. This is shown also by the fact that where a new well was made the seedlings watered 

 from it remained free, while those watered from the old well became diseased. This and other cases 

 cited tend to show that sound plants set on healthy land may become diseased by the use of infected 

 water. 



By use of 1 to 1,000 potassium permanganate such water is disinfected and is not too concen- 

 trated for watering transplants, but would burn seedlings in the bed. It has been communicated to 

 Honing that 0.05 per 1,000 (50 grams per cubic meter) does not burn the seedlings. In using this 

 substance it must be remembered that in water rich in organic matter potassium permanganate soon 

 loses its disinfecting power and greater quantities must be used, concerning which no general rule 

 can be laid down. 



There are some plantations on which it is not possible to grow healthy seedlings, all of the soil 

 being infected. If one must make seedlings on such land, then not only the water used but also the 

 soil of the seed-bed itself must be disinfected. Sound seedlings are of the utmost importance, because 

 a large percentage of the dead plants have come from infected seedlings. 



Capsicum is less susceptible than Solatium species. In one case a tobacco strain which failed on 

 Capsicum (18 plants) became infectious to Capsicum after passing it through Mucuna. 



(3) REPORT ON THE SLIME-DISEASE TESTS OF 1911. 



General infection of the soil is probably less common than has been supposed. The tobacco has 

 not died on all the flooded lands. 



The disinfections with chlorid of lime and with potassium permanganate yielded no striking 

 results. 



Water from 2 1 wells was examined, of which 7 on 5 plantations yielded the slime-bacteria. 



Bacillus solanacearum Smith has now been isolated and cultivated out of seedlings or field tobacco 

 from 17 plantations. While the cause of the slime-disease is the same on all the plantations, the 

 circumstances under which infection takes place are very different and are known only in part. 



(4) DESCRIPTION OF THE DELI STRAINS OF BACILLUS SOLANACEARUM SMITH, THE CAUSE OF 



THE SLIME-DISEASE. 



The most important questions resulting from a study of the literature, the inoculation experi- 

 ments on tobacco and rotation of crops, and from a study of the cultures are the following: 



(a) Is there to be found a series of foodstuffs, by means of which this organism can be distin- 

 guished from others by growth or absence of growth; also how to separate virulent from non-virulent 

 forms? 



(b) Is the slime-bacterium in Japan, which has been described under another name (Bacillus 

 nicotianae Llyeda), possibly the same as that in America and in Deli, so that means of combating it 

 elsewhere recommended can be tried here? 



(c) Is perhaps Bacillus sesami Malkoff in Bulgaria [see p. 216] also the same bacterial sort as 

 that in our tobacco and our Sesamum? 



MORPHOLOGY. 



Form and size. The Deli strain of Bacillus solanacearum is somewhat more variable than Smith 

 and Uyeda have announced (see pp. 193, 238). 



