184 



BACTERIA IN RELATION TO PLANT DISEASES. 



escape Scylla only to fall into Charybdis. It may be that his organism varies in all 

 sorts of ways, but he is by no means to assume this. Every hypothesis must be tried 

 in the reducing fire of exact experiment. 



Probably the best acquirement a student can get from his years of training is 

 a spirit of self-distrust leading to habitual caution in the drawing of conclusions 

 and the making of general statements. Such a spirit 

 will preserve him from many foolish statements and 

 will enable him to serve his generation to the best of 

 his ability. He will not go far, however, without a 

 tremendous earnestness, an indomitable energy, directed 

 in proper channels. Let him concentrate this energy, 

 the most priceless of all human attributes, and attack 

 specific problems, one after another or a few at a time ; 

 not all at once. Honesty, industry, and self-reliance, 

 tempered with the self-distrust already mentioned, will 

 then carry him very far on the road he desires to go. 

 Finally, the student should remember that the ideal 

 man of science, and to a large extent also the actual 

 man of science, is a modest man, always inclined to be 

 cautious, always willing to revise his conclusions in the 

 light of fresh evidence, generally plain-spoken, always 

 an enemy of shams, and never offended by frank and 

 honest criticism, preferring the white light of truth to 

 the plaitdits of the multitude. 



A FINAL CAUTION. 



Probably more mistakes arise from failure to 

 carefully check up the work behind one than 

 from any other source. What is meant by this 

 can be explained in a few words, 

 by means of a series of examples. 



(i) I make subcultures from 

 a poured-plate colony. The first 

 subculture is on slant agar, the 

 second is from the agar into 

 beef-broth, the third is from the 

 beef-broth into potato - broth, 

 and from the latter I propose 



to inoculate a plant. The in- 



Fig. 146.* 



*FiG. 146. Apparatus for removing water from tissues with a minimum of injury. The speci- 

 men is placed on the wire carrier at X in water. The tube at the right also contains water. Alco- 

 hol (95 per cent) is then poured into the funnel and allowed to pass into the apparatus drop by 

 drop. Its perfect diffusion through the water is obtained by making the basal ends of the carrying 

 tubes flaring or funnel-shaped. By gaging the time between drops the alcohol may be substituted 

 for the water, slowly or rapidly, in any desired time. About one-third actual size. 







