Mcculloch's cauliflower spot: technic 311 



For the inoculations, growing cabbage and cauliflower 

 plants 6 to 12 inches high may be used. These, preferably, 

 should be made in infection cages, by spraying the under surface 

 of the leaves with water containing suspensions of young agar- 

 streak cultures. If proper conditions are obtained, good in- 

 fections in large numbers should be available for study by the 

 end of the first week. By ''proper conditions" are meant: 

 (1) moist conditions for 48 hours; (2) growing plants; (3) 

 temperatures under 29°C. (84°F.); and (4) use of bacterial 

 cultures which have not lost their virulence or become attenu- 

 ated by harmful laboratory conditions. Miss McCulloch 

 several times obtained numerous infections on both cauliflower 

 and cabbage plants by spraying, but none in hot weather and 

 none or few with the descendants of old cultures. It is possible, 

 however, that some of her isolations may represent feeble strains 

 of this parasite. 



Under our rather dry hothouse conditions secondary in- 

 fections were not observed. That is, the infections were 

 limited to the leaves actually sprayed. 



Determine 



For the organism. Morphology. — ^Size in microns. Ab- 

 sence of endospores (try heat and spore stains). Motility 

 on the margin of a hanging drop. Persistence of motility 

 in old cultures. Number and distribution of flagella (use 

 van Ermengem's or Hugh Williams's method). Conditions 



"B" strains were not clouded in 18 hours. 

 After three days there was faint clouding in "B'' strains. 

 In six days the growth in "B" strains is less than in room temperature 

 cultures in 18 hours. 



(3) 29.5-30.5°C. 



"A" strains were slightly clouded in 24 hours. 



"B" strains not clouded. 



"B" strains not clouded in four days. 



(4) 30-3 1°C. 



"A" strains clouded faintly in 24 hours. 

 "B" strains not clouded in four days. 



