. Carnegie Institution of Washington publication. 170 BACTERIA IN RELATION TO PLANT DISEASES. dale's conception of this organism, at a time when the air was full of talk of Cohn's researches, is shown in fig. 140. Dallinger & Drysdale's drawings were made from unstained material, and there is no doubt that these expert microscopists actually saw what they figured, viz, a schizomycetous organism provided with one polar flagellum and belonging to the family Bacteriaceae. Dallinger afterwards care- fully measured the diameter of the flagellum many times over in unstained material, grown in Co
. Carnegie Institution of Washington publication. 170 BACTERIA IN RELATION TO PLANT DISEASES. dale's conception of this organism, at a time when the air was full of talk of Cohn's researches, is shown in fig. 140. Dallinger & Drysdale's drawings were made from unstained material, and there is no doubt that these expert microscopists actually saw what they figured, viz, a schizomycetous organism provided with one polar flagellum and belonging to the family Bacteriaceae. Dallinger afterwards care- fully measured the diameter of the flagellum many times over in unstained material, grown in Cohn's fluid. As bearing on the question whether Ehrenberg could see the flagellum of an unstained bacterium with the microscopes at his disposal, it is inter- esting to note Dallinger's statement that Koch could not see the unstained flagellum of Bacterium termo because he used "low-angled glasses, which are incompetent to that ; Another remark of Dallinger is also pertinent. "I have learned," he says, "from experience that there is as great a diversity in different individuals in the sensitiveness of the retina as there is in sensitiveness of the olfactory or auditory ; The writer's own conception of Bacterium termo is shown in fig. 141. These organisms are green-fluorescent species cultivated in Cohn's solution, from water into which beans had been thrown in the manner described by Cohn. The very distinct flagella were stained by Lowit's method. The particular species from which this was obtained did not / liquefy gelatin. * 600 ca To the writer, then, the genus Bacterium is Bacterium lg' '* (Cohn emend.), and is based on the morphology of the green-flnorescent organisms, i i capable of growing in Cohn's nutrient solution and called by him Bacterium tcrnioS. It corresponds ) j to Migula's genus Pseudonumas, for which name it ( should be substituted as a proper generic name for ^-~, V "P * i ^^ , straight or slightly curve
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