WILT-DISEASES OF TOBACCO. 



225 



With exception of a yeast no fungi have been observed. 



The cause of the disease will remain in the ground in the absence of tobacco cultivation for 8 

 years or more. Exhaustion of the soil is not an explanation, because in splendid high tobacco on land 

 which has had little or no fertilizer the disease occurs. 



Bad drainage certainly favors the spread of the disease, but is not the cause of it, and it may 

 occur to a serious extent on the best-drained lands. 



Degeneration of the Deli tobacco can not be the cause. Plants which on only moderately good 

 ground and often under unfavorable circumstances make stems 2 meters high, blossom, fruit, and set 

 seeds 90 per cent of which will germinate, can not be run out. 



On the east coast no plant has been suspected more than Albizzia, but this can not be the cause 

 of the tobacco disease.* There are places where Albizzia has persisted, where none or little of the 

 tobacco disease occurs, and on the contrary there are lalangf soils where 80 to 90 per cent has been 

 killed. 



" In my opinion the slime-sickness is a bacterial disease." 



The first thing to be done was to determine whether the disease could be reproduced with the 

 bacteria present in all the slime-sick plants. Stems of such plants were chopped fine, mixed with 

 earth, and then placed under 24 young plants, of which 15 contracted the disease, the presence of the 

 bacteria in them being controlled by microscopic examination. Of the 24 control plants none became 

 diseased. 



The juice of the sound pith of tobacco is slightly acid, that of diseased plants is alkaline and blues 

 red litmus paper, but if the decay continues until the stems become hollow, it may again become acid. 



If one makes transfers from the nerves of leaves which have recently begun to droop, and as high 

 up as possible on the stems, frequently one may obtain pure cultures of the slime-sickness bacteria. 

 The bacteria occur first in the large cells of the bundle, later in the phloem and water vessels. 



With bacterial cultures, so obtained, inoculations were made. On May 23, 12 rows of young 

 tobacco plants, 25 in each row, were treated as follows: 



i. Control. 



a. Plants dipped into a dish containing about 2 liters of water in which a bacterial culture was poured, and then 

 planted. 



3. After the planting, the ground around the seedlings was watered with a very dilute culture, about 10 c.c. to a 



watering pot. 



4. Control. 



5. Control. Injection into the stem, 2 days after planting, of the same sterile bouillon that served for the 



bacterial cultures. 



6. Before planting each plant was injected at the crown with a pure culture in bouillon. 



7. Control. 



8. The day after the watering of the soil with a dilute pure culture each plant-hole was watered with 0.4 gr. 



potassium permanganate dissolved in 0.5 liter of water, and a half hour later the plants were set out. 



9. The stems received injection of a pure culture 8 to 10 cm. above the crown, where a leaf had been pulled off 



for the purpose. 



10. Injection of a leaf-nerve by means of a hypodermic needle and higher up near the leaf top, 3 or 4 prirks. 



1 1 . The leaves, and consequently the earth, were watered with a diluted pure culture. 



12. The plant-holes were watered with a dilute pure culture and the plants were set out one day later. 



The number of diseased plants were as shown in table 23. 



TABLE 23. Result of Honing s First Inoculations. 



"Na deze proeven blijft er, voor mij ten minste, geen spoor van twijfel over aan den bacter- 

 ieelen aard der slijmziekte." 



The disease is hastened by introducing the bacteria into the plant, but in the end it enters the 

 plant from the soil. 



The failure of a portion of the checks is attributed to a natural infection of the soil, the location 

 having proved to be a bad one, as shown by results in three rows of tobacco planted near these some- 

 what earlier and a considerable part of which succumbed. 



'This has reference to the fact that a disease of unknown origin has destroyed many thousands of Albizzia trees, 

 formerly extensively used as a shade plant for various cultivated crops, but now generally abandoned. 

 fA coarse grass. 



