270 Early Studies in Bacterial Plant Diseases 



verification and rechecking was then: " Determine what acid is 

 produced by the breaking up of the sugars." Second, " Repeat 

 experiments, growing bacillus in juice of parenchyma, to deter- 

 mine if the acid actually retards growth, comparing with cultures 

 in potato broth and beef broth. . . ." When repeating his thermal 

 death point experiments, he wanted to " determine whether heat 

 just below thermal death point only paralyzes or actually destroys 

 the majority of the bacilli." 



From experiments and culture study made to see whether the 

 germ would grow only, or at all, on alkaline media, Smith later 

 evolved a theory of alkalinity of vessels. A memorandum read: 



The fluid in each one of these six tubes is plainly alkaline to neutral 

 litmus although the media was plainly acid on the start. It is probable 

 that an acid is also present for on warming the blued litmus paper in 

 the bottom of a deep beaker over a gas flame the blue color quickly dis- 

 appears and the spots are then redder than the rest of paper as if from 

 presence of some acid. If this is true then this germ breaks up grape sugar 

 (muscle sugar) and will probably grow in closed end of fermentation tube. 

 Anyway the germ is a plain alkali producer and this alkali is readily 

 driven off^ by heat i. e. it is ammonia. 



Dr. Smith has elaborated the vast detail of his many experiments 

 made with this organism.'" What is presented here indicates his 

 thoroughness and foresight in such investigations. On November 

 27 he observed under the microscope in a hanging drop from a 

 broth culture a number of rod-like organisms with rounded ends 

 and the " exact appearance of bacteria, but highly refractive, 

 like spores." He examined them with the polariscope. They 

 were not crystals. Arthrospores ? he asked. Settlement of this 

 question was the sixth among the thirty points before conclu- 

 ding his original studies of this disease. He restudied his notes 

 on the durability of the organism on various media. He inves- 

 tigated other species of plants susceptible to the malady. His 

 experiments were made under widely differing sets of environ- 

 mental conditions, all with a view to establishing the disease's 

 etiology. In 1893 he had noticed on diseased cucumber vines 

 several insects which might be carriers of the infection, and during 

 the next years he proved its transmission by the striped beetle 

 {Diabrotica vittata) . Many experiments involved also the squash- 



^'^ Bacteria in relation to plant diseases, op. cit., 2: 217-282, etc. 



