rj.ORiPA AND Calu-ornia Lauoratorif.s 269 



Every experiment yielded up data of the organism's biology of 

 development and action. Culture media had four-fold uses: "^ to 

 isolate organisms from mixtures or directly from diseased plant 

 tissues, to grow organisms without loss of virulence over long 

 periods, to serve the purposes of differential description, and to 

 aid in chemical analysis. Smith, in " the first treatise of its kind 

 in the world," an introductory text book,"" not a monograph, on 

 bacterial diseases of plants, stated in 1915-1920 some objectives 

 he had maintained in differential descriptive cultural study for 

 more than a quarter of a century. Said he: 



What we seek here are media that will bring out not necessarily good 

 growth, or any growth at all, for that matter, but differences in behavior 

 when a variety of bacteria are tested in it, that is, changes in gross appear- 

 ance, morphology, pigmentation, precipitates, pellicles, crystals, weak vs. 

 dense clouding, medium reactions (acid, neutral, alkaline), using neutral 

 litmus and phenolphthalein, etc. — and here a medium generally neglected 

 by bacteriologists may be just the one needed. . . . Often, when the 

 colonies of two organisms look exactly alike on plus 15 peptone-beef agar, 

 we try potato agar, prune agar, string-bean agar, starch agar, whey agar, 

 or some kind of gelatine medium, and find a difference. 



By 1895 Smith found himself able to improve his technical 

 proficiency in the study of plant bacteria. It was perhaps as late 

 as November 1894 before he began to refer in his research memo- 

 randa to the cucumber " germ " as Bacillus tracheiphilus. During 

 this month he increased his acidified broths to at least five or six. 

 Really not until this month did he invent his own formulas for 

 beef and potato broth cultures. It was during this month that 

 he concluded that B. tracheiphilus " splits up glucose forming an 

 acid." As well as studying the organism's growth and behavior, 

 he was exploring its nature and needs, its range of tolerance to 

 acids, alkalies, salts, sugars, N-compounds, alcohol, et cetera. 

 In the year 1894 he completed his first technical description 

 of the plant pathogen B. tracheiphilus. At this time, he must 

 have believed that he had satisfied the requirements of Koch's 

 canons. But not until 1895-1896 did he prepare his last elaborate 

 outline of " Things which must be done before I can close out 

 my experiments on Bacillus tracheiphilus." One of the points for 



°* Uses of culture-media, Intro, to Bact. Dis. of Plants, op. cit., 99-100. 

 ^"Ibid., v-vi, 99-100. 



