212 



BACTERIAL DISEASES OF PLANTS 



be kept under observation for three months or more. The 



spreading colony is the more virulent one. 



Agar-plate cultures, especially when 

 made directly from the plant, should be 

 kept under observation for at least fifteen 

 days. Colonies are seldom ready for ex- 

 amination earlier than the eighth day. 

 Agar titrating +8 or +10 on Fuller's scale 

 is better for plate cultures than + 15 or 

 that which is more acid. In general, in- 

 oculations will be more successful if made 

 with sub-cultures from recent isolations 

 rather than with those long in the labora- 

 tory. They should be of the same sum- 

 mer, if possible. 



^" 



^ 



FIG. 154. Green 

 t o m a t o fruit oozing 

 A planobacter michigan- 

 ense around the pedi- 

 cel. The result of a 

 stem inoculation. 

 Photographed from al- 

 coholic material. _, _ .. 



FOR THE ORGANISM. Morphology. 



Size in microns, form, aggregation of elements. Examine for 

 motility, stain with flagella stains, search for endospores, stain 



Determine 



FIG. 155. Tomato plant infected with a pure culture of Aplanobacter michi- 

 ganense through the soil by way of broken roots. Inoculated Nov. 17, 1910. 

 Photographed Dec. 21, 1910. This also shows irregular wilt of leaflets. 



viscid cultures for a capsule; try Gram's stain; acid-fast stain. 

 Any evidence of involution forms? 



