72 HISTORY AND CAUSE OF THE COCONUT BUD-ROT. 



GROWTH ON STARCH MEDIA. 



Experiment 1. — Both the coconut organism and Bacillus coli were 

 grown on potato cylinders and after 18 days were tested with an 

 iodin potassium iodid solution for amylodextrin as follows: 



Coconut No. 1 showed distinctly the red purple on the addition of Lugol's iodin. 

 Some blue fragments indicated that not all the starch had been converted. 



No. 5 showed a good red-purple reaction and also abundance of blue. 



Bacillus coli showed red purple almost throughout the cylinder, there being only a 

 few fragments of blue. 



Check-potato cylinders showed only a bright Prussian blue on the addition of Lugol's 

 iodin. 



Experiment 2. — A nutrient solution consistmg of 1 per cent peptone, 

 2 per cent dextrose, and 0.1 per cent cornstarch was made up, and a 

 number of tubes were inoculated with the coconut and Bacillus coli 

 cultures. After incubation for 17 days at 22° C. the tubes were tested 

 for the presence of starch. As it was found in preliminary tests that 

 a small amount of Lugol's iodin gave only a transitory blue, the exact 

 amount used for the test was determined. It was also found that a 

 tube showing a good test for one minute or five minutes might be 

 entirely colorless after a longer time. One minute was selected arbi- 

 trarily as the limit of time for the color reaction to persist. It was 

 found that from four to five drops of the iodin solution were necessary 

 to give the Prussian blue starch reaction in a check tube and have it 

 persist for one minute. Among the culture tubes it was found that, 

 on the average, about 80 drops of the iodin solution were necessar}^ 

 to make the dark color persist one minute. Wliile the test gave the 

 bright blue in the check tubes, in all the culture tubes the color 

 reaction was a red purple, or on long standing and adding more iodin 

 a red or rich brown color. There was no evidence of the blue starch 

 reaction in the culture tubes except on examination with the micro- 

 scope. By this means blue particles could be found, but only in small 

 quantities. This experiment demonstrated clearly that the starch is 

 affected by the organism and in this particular case using a dextrose- 

 peptone medium nearly all of the 0.1 per cent starch was converted. 



Experiment 3. — Cultures of the coconut organism and Bacillus coli 

 were made in three different media as foUows: (1) Two per cent 

 peptone plus 0.05 per cent NaCl plus 0.1 per cent potato starch; (2) 

 the same with the addition of litmus; (3) a tliird medium similar to 

 the first with the addition of dextrose. Tlie purpose of this experi- 

 ment was to ascertain if the action of the starch was independent of 

 any sugar present. Litmus was added to the first medium to serve 

 as a check to indicate the presence or absence of acid formation. If 

 any acid were formed it would be from the starch. No titration was 

 made of these cultures. It was assumed from other experiments 



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