336 



BACTERIAL DISEASES OF PLANTS 



bolls and watch. Determine the effect of the disease on young 

 seedlings, inoculating cotyledons and hypocotyl by means of 

 needle pricks. Describe the disease, but not out of this book. 

 Histology. Embed, section and stain young leaf-spots, 

 18th day and earlier. Can you find distinct evidence of stoma- 



FIG. 258. Tubes of Loffler's solidified blood serum inoculated from bouillon 

 with Bacterium malvacearum (Arizona organism) and with Bacterium phaseoli 

 (Idaho organism) for comparison; Nos. 1 and 2 streaked April 12; 3 to 6 streaked 

 April 21. Photographed May 3, 1919. No. 1, liquefied; Nos. 3 and 4, partly 

 liquefied; Nos. 2, 5 and 6 not liquefied. No. 2 is drying out on right side. 



tal infection? Stain with carbol fuchsin or amyl Gram. In 

 the same way study early stages of the disease on stems and bolls. 

 Does a brown stain accompany this disease? 



Variability. Does this disease ever kill the plant? Ever 

 render it unprofitable? Attack some varieties to the ex- 

 clusion of others? Appear to be much worse some seasons 



