136 BACTERIA IN RELATION TO PLANT DISEASES. 



In tubes of peptonized beef bouillon at the end of about 18 days (room- temperatures of 

 spring) there was a feeble, whitish rim, a well-clouded fluid, about 10 mm. breadth of pale 

 yellow precipitate, and no distinct pellicle (stock 791). Repeated in 1908 in stock 3398. 

 At end of 10 days, when notes were taken, the tubes were well clouded with a moderate 

 amount of pale yellow flocculent precipitate. There was also a well-defined but rather 

 scanty whitish rim. 



In a fluid prepared by grinding green cabbage-leaves, taken from old, slow-growing hot- 

 house plants, and extracting the juice under pressure without addition of water, there was a 

 very prolonged and copious growth without retardation. A portion of this fluid was steril- 

 ized by forcing it through a Chamberland filter and the rest by discontinuous steaming. 

 The reaction of each was +40 on Fuller's scale. Bad. phaseoli and Bact. campestre refused 

 to grow in this fluid, but when it was solidified by adding agar-flour, Bact. campestre grew 

 upon it very copiously and for a long time, although it was started with much difficulty. 



Bact. stewarti was retarded at first, but afterward made a prolonged and copious growth 

 in three out of four tomato juices undiluted with water. In the fourth it refused to grow. In 

 stocks 333 and 334, obtained respectively by squeezing green full-grown or nearly full-grown 

 fruits, and small green fruits (one-twentieth to one-quarter grown) there was a good growth 

 on the fifth day. The acidity of these two stocks was respectively +55 and +59 of Fuller's 

 scale. Instock33i, which was the steamed juice of ripe fruits, there was a greater retardation, 

 the tubes becoming clouded between the eighth and fifteenth day. The acidity of this med- 

 ium was +64. Stock 332, in which the organism would not grow, was +68, i. e., a little 

 more acid. It consisted of the steamed juice of fruits which were yellowish green, i. e., full- 

 grown and beginning to ripen. It would seem, therefore, if we may trust the titration, that 

 +64 is near the limit of toleration for the acid of the tomato.* Bact. campestre and various 

 other organisms refused to grow in these fluids. 



In a 2 per cent agar containing the juice of 10 grams of acid mulberry fruits in 490 c.c. 

 of water (autoclaved) Bact. stewarti made no growth, i. e., 8 Petri-dish poured plates made 

 with yellow slime from each of two recently infected plants. On the 16 plates not a colony 

 appeared. That the organism was living in each case was shown by subsequent cultures 

 from the dilutions. The work was defective in that the acidity of the agar was not deter- 

 mined by titration. Two mulberry agars were in the laboratory at the time, one made from 

 green fruits of Morus alba, the other made from ripe fruits of Morus rubra, but there is no 

 record as to which was used. 



In a potato broth of half strength (i : 4) which titrated +30 on Fuller's scale, Bact. 

 stewarti grew readily, while Bact. phaseoli and Bact. campestre refused to grow, and Bact. 

 hyacinthi was much retarded. Bact. stewarti also grew in this broth without retardation 

 when sufficient malic acid had been added to it to make it +45. Bact. hyacinthi, Bact. 

 phaseoli, and Bact. campestre, refused to grow in this fluid. Bacillus amylovorus and Bact. 

 dianthi grew in it readily. 



This experiment was repeated in 1908, using Bact. stewarti from three sources and dilute 

 potato broth rendered +41 by malic acid. Each grew well. The tubes each received two 

 3-mm. loops from peptonized beef bouillon 3 days old. Each was well clouded at the end of 

 48 hours. On the seventh day each tube had a copious pale precipitate and a pale rim. On 

 the eleventh day the tubes were still well clouded with a pale flocculent precipitate and a 

 pale buff-yellow rim, i to 2 mm. wide. 



In beef broth concentrated by boiling until it was quite yellow and strongly acid (+80), 

 Bact. stewarti grew for a long time and very luxuriantly, but clouding did not appear until 

 the eighth day, although the inoculation was from a solid culture. In this medium the fol- 

 lowing bacteria refused to grow : Bact. hyacinthi, Bact. phaseoli, Bact. campestre, Bacillus 

 amylovorus. 



*This acid is said to be tartaric acid. Experiment repeated in 1913: No growth in +45 or +60. 



