June, 1913.] The Mosaic Disease of the Tomato. i6i 



of this theory are. Maver (1S8(3); Iwanowski (1S92) (a) (1901, 

 1903); Prillieux and Delacroix (1S94); Marchal (1S97); Koning 

 (1899 a, 1900 b); Breda de Haan (1S99); Behrens (1896). 



Mayer (1886), was perhaps one of the first to suggest bacteria 

 as the cause, saying that the disease is of a bacterial nature. 

 He says, however, that the organism had not been isolated and 

 that nothing is known about its form. Breda de Haan (1899) 

 as quoted by Hunger (1905, p. 262), claims it possible to obtain 

 a bacterium from the plant tissues and grow it in culture. Pril- 

 lieux and Delacroix (1894) state that a bacillus 0.7 mic. long 

 was associated with grey or yellow spots occurring on tobacco 

 leaves, which they took to be mosaic disease. Marchal (1897), 

 speaks of finding colonies of bacteria which grew in chains and 

 were yellow colored. He claimed that infection occurred in the 

 seed-bed. According to Hunger (1905, pp. 259-60), however, 

 Iwanowski was the first to find bacteria in connection with mosaic 

 disease and certainly his work is the most complete and most 

 convincing that has appeared in support of the bacterial theory. 

 In (1899, p. 253) he reports, "From a poured plate in which one- 

 half drop of mosaic diseased juice was applied, ten transfers 

 from different colonies were made to test tubes, and from each 

 of these, three plants were inoculated. From numbers 6 and 9, 

 two plants showed symptoms of typical mosaic disease within 

 2 or 3 weeks." In a second preliminary paper (1901, p. 148), he 

 says, "Therefore a specific bacterium is the cause of mosaic 

 disease — . " He claims that its discovery is merely a question 

 of proper microtechnique. His final paper (1903) discussed 

 various bacteria obtained from mosaic disease and gives photo- 

 graphs showing them as they occur in host cells. According to 

 him the reason that Beyerinck was not successful in his attempts 

 in isolating bacteria by applying juice to agar tubes, was because 

 it was first filtered, which he says prevented growth. He states 

 (p. 37), "One of the simplest reasons for not having been able 

 to grow this organism from filtered juice is, that the microb is 

 incapable of growing in pure ciilture and only develops in con- 

 nection with other bacteria in the soil and in the living plasma 

 of the plant." Such filtered juice, however, will produce the 

 disease. This, he explains, by saying, that the microb forms 

 resting spores. Upon this assumption he believed the microb 

 could be grown only from the vegetative form. He used agar 

 plates and succeeded in obtaining two colonies which produced 

 mosaic disease when reinociilated. He does not mention how 

 or where he made his inoculations and his controls do not appear 

 to be adequate. The percentage of disease produced by his 

 artificial inoculations was small as compared ^vith ordinary juice 

 inoculations; this, he explains as due to a reduction in virulence, 

 as often is the case when bacteria arc grown on artificial media. 



