BACTERIAL CANKER OF TOMATO I CAUSE 207 



plates is very slow, often so slow as to discourage isolations. It 

 is sensitive to heat, acids, even of beef juice (Fig. 160), and sodium 

 chlorid. It endures drying well. It gradually loses virulence 

 on culture media. Litmus agar containing dextrose is reddened. 

 It does not grow in Cohn's solution or in Uschinsky's solution. 

 The slime is apt to be viscid, both on potato and on agar. It is 

 also viscid in certain sugar solutions. Is it ever viscid in milk? 

 Spieckermann in Germany has described a potato disease 

 of slow development but considerable importance, due to a slow- 

 growing, yellow, non-motile schizomycete which I suspect to be 

 this organism, or one closely related to it. This he has named 

 Bacterium sepedonicum (A pi. sepedonicum in my terminology.) 



FIG. 147. Tomato stem in cross-section showing the center of an incipient root 

 honeycombed and destroyed by Aplanobacter michiganense. 



Technic. Because of the slow development on poured plates, 

 isolations from the plant may be made in deep Petri dishes by 

 parallel streaks on slices of steamed potato, where the last 

 wipings of the needle (there should be 6 or 8) should yield single 

 colonies from which poured plates and sub-cultures may be made. 



The upper part of stems of young rapidly growing plants 

 may be used for inoculations which may be by needle-pricks from 

 young potato cultures. If the organism is virulent, results will 

 begin to appear in 10 or 15 days, but the inoculated plants should 



